The Animal Mind: A Textbook of Comparative Psychology

hypothesis which we shall discuss in Chapter XI. An unknown force, he concludes, guides the bee in its homing flight (51). Von Buttel-Reepen believes that visual memory will explain all the facts; that the bees were not disturbed by the altered appearance of their hive because they knew their way so thoroughly that nothing could disturb them by the time they had come so nearly home. The visual memory required is, he admits of a peculiar sort, which we shall consider in a later chapter. The odor of the hive does codperate with vision in certain cases; when a stock of bees has been moved without their knowledge, they fly out without making any “‘orienting flight,” as they commonly do on leaving a new place, a fact that is one of the evidences for the visual memory theory. Nevertheless, many of them succeed in finding their way back, and then, if their hive is placed among a number of others, von Buttel-Reepen thinks they ‘‘smell” their way back to the right one. He mocks at Bethe’s unknown force, on the ground that it must sometimes lead the bee to the hive and sometimes back to the place where food. has been ‘found (115). Bethe attempts to answer this by saying that the force acts in codperation with the physiological condition of the animal; the laden bee follows it to the hive, the bee with the empty crop is led back to the food supply (52). Of course one may say what one pleases about the modus operandi of an unknown force without fear of disproof, but also without carrying much conviction.

That a mysterious sense of direction exists in the bee is concluded by Bonnier (97) from the following evidence. He first showed that bees whose eyes had been covered by pigmented collodion could go directly to their hive if they were not more than three kilometers away. Smell, however, or muscular memory, might account for this. He then attempted to demonstrate that smell was not an essential factor in guiding bees. He placed two stands carrying honey, one 200 meters, the other six meters from the hive, and marked the bees that visited each stand, proving that a given bee almost never went to both, but continued to visit the stand where it had first found honey. Here, however, sight might have been the determining influence. Wagner (751) thinks that bees in the neighborhood of the hive are influenced by visual landmarks, but that in their longer flights they depend on a sense of direction, which seems however to be a form of visual memory. On the whole, smell would appear to be only one factor, and not a very important one, in guiding the flights of bees.

The nest smell, which characterizes each hive and prevents the reception of strangers, who are treated precisely as by ants in similar circumstances, is composed according to von Buttel-Reepen of the following odors: the individual odor of different workers; the family odor, common _ to all the offspring of the same queen; the larval smell and food smell; the drone smell, the wax smell, and the honey smell. There are various ways in which the mode of reaction to a foreign nest smell is modified. If two bee stocks are placed side by side, and one has the queen and entire brood removed, it will go over to the other stock and be _kindly received. One can understand that the attraction of the queen and brood odor may overcome the tendency of the foreign nest smell to repel the invaders, but it is harder to see why the more fortunate stock should allow itself to be invaded. Further, a bee laden with honey can get itself received by a foreign steck that has exchanged

hives with it, where an unladen bee is attacked; here the smell of the honey may overcome the foreign smell. As is well known, two alien stocks may be united by sprinkling them with some odorous substance. The queen odor is the strongest factor in the nest smell; in swarming it overcomes the tendency to return to the old nest, and queenless swarms will join themselves to foreign swarms having a queen. The apparent attention paid to the queen while laying eggs, the gathering of workers around her trilling their antenne toward her, suggest strongly that her odor is pleasant to them. The queen, herself, however, is perfectly indifferent to any foreign nest smell, and will beg food of any bee, even those which are angrily crowded around her cage in a foreign hive. Drones also will go from stock to stock, and are always peacefully received until drone-killing time begins. It has usually been supposed that the unrest displayed by a bee stock when deprived of its queen is due to the absence of the queen odor, and it seems almost certain that this must be a powerful influence, though von Buttel-Reepen thinks it is not the only influence, for he has observed that if the queen be replaced in the honey space, removed from the rest of the hive, the bees will quiet instantly, before the smell has had time to diffuse itself. Also, bees sometimes behave as if they had lost their queen when she is only put in a cage, and her odor is perfectly accessible (115).

It is clear that bees as well as ants are capable of distinguishing a considerable number of smell qualities. Probably the same thing is true of the social wasps. In the solitary wasps, however, we find less evidence of a highly developed sense of smell, or rather of a great variety of smell reactions, and the solitary bees are very likely less influenced by smell than the social bees. In the interesting study of the solitary wasps by Mr. and Mrs. Peckham, it appears that sight plays a far more important réle than smell for these insects, and the return to the nest in particular seems to be almost entirely an affair of sight (572, 573). In gen- ‘eral, the greatest development of qualitative variety in the sense of smell is found in the social Hymenoptera, and is probably a product of the social state. Perris, however, noted that the solitary wasp Dinetus was much disturbed in finding its nest hole if he had placed his hand over the hole during the wasp’s absence, and thought the odor of his hand was distracting to the insect (574).

~~ Although the vertebrates stand at the head of the animal kingdom, yet in point of complexity of structure and behavior the lowest vertebrate is far below the highest members of the invertebrate division. When we undertake to study the responses to special stimulation displayed by this same lowest vertebrate, the little Amphioxus or lancelet, it is like going-back to the earthworm. The only kind of evidence that contact, chemical, and temperature stimuli produce specific sensation qualities is found in the fact that sensibility to them is differently localized, and may be independently fatigued. To weak acid, the head end of the animal is most sensitive, the posterior end less, the middle least; to contact with a camel’s-hair brush, the two ends are equally sensitive and more so than the middle; to a current of warm water the order of sensitiveness is: head end, middle, posterior end (541). For fishes, as for all aquatic animals, the distinction between smell and taste becomes obscure. The neighborhood of food not in actual contact with the body seems to stir

fish to activity, but not to direct their movements. Bateson (25) and Herrick (297) both obtained evidence of this; Nagel, on the other hand, declares that fish do not perceive food at a distance except by sight, and that the function of the first pair of cranial nerves in these animals must remain uncertain (522). The well-developed character of these “olfactory” nerves and lobes, whose function in higher vertebrates is certainly connected with smell, would argue against the supposition that smell can be wholly lacking in fishes. It is generally agreed that a contact food sense exists in fish; Nagel, however, holds that its organs are situated only about the mouth (522), while Herrick has good experimental proof that fishes which have ‘terminal buds,” structures resembling taste buds, distributed over the skin, are also sensitive to food stimulation applied to different regions of the skin. He thinks that Nagel’s negative results were due to the fact that instead of food stimuli in his experiments he used chemicals with which the fish would not normally be acquainted (297).

Parker (546), experimenting with catfish and the young of a species of lamprey, found the whole body surface more or less sensitive to salt, acid, and alkali; the body of the lampreys was sensitive also to quinin solution, but that of the catfish was not; neither animal displayed skin sensitiveness to sugar solution. Cutting the nerve supply to the olfactory organs, the lateral-line organs (see page 128), and the taste buds failed to abolish skin sensitiveness, which Parker therefore concludes must depend on free nerve endings in the skin. He distinguishes three forms of chemical sensibility in these lower vertebrates: common chemical sensibility, for which free nerve endings are the organ; taste, dependent on the taste buds; and smell, dependent on the olfactory nerves, and responding to much

more dilute solutions than the other two, thus being capable of acting as a distance sense (550). A number of species of fish have been shown to possess smell, by demonstrating that they can discriminate between small bags filled with food and similar bags stuffed with inedible substances, and that this discrimination is lost when the olfactory nerves are cut or the nostrils are closed (547, 142). Shelford and his associates (673) have thrown light on a very interesting problem in animal behavior, the migrations of fish. It is well known that salmon return to fresh water to spawn, ascending rivers, and that other fish perform migrations that are of great economic importance to the fishing industry. Shelford has demonstrated that fish are very sensitive to slight variations in the chemical constitution, the salinity, for instance, of the water in which they live, and their responses to such changes may well account for all their wanderings.

Among amphibians, the spotted newt seems to show a relation between smell and the “‘common chemical sense” not unlike that existing in fishes. The olfactory nerves seem to be required for the discrimination of food. When chemicals are applied to the body, the head end is much the most sensitive region, even when the olfactory nerves are cut. Acids and alkalies cause very marked reactions; salt is less effective and sugar not effective at all (629). Cole (135) studied the time required for the reflex withdrawal of the hind legs of leopard frogs when four chlorides, those of ammonium, potassium, sodium and lithium, were applied in solution. He found that the speed of reaction corresponded to the order in which these salts affect the human sense of taste. That a common chemical sense, and not pain, was involved in these skin reactions was indicated by the fact that they persisted when ordinary pain reactions,

to pricks, were abolished by cocaine. Risser (638) reports that while sight seems to be more important than smell in determining the mature toad’s reactions to food, tadpoles failed to distinguish packets containing food when their nostrils were plugged. Immature Amblystomas, which in the normal condition react positively both to motionless food and to moving inedible objects, lost the first type of response when their nasal pits were removed, and the second type when their eyes were operated on (112). ~

In birds sight and hearing are so well developed that the chemical sense assumes less importance. Birds seem to have a sense of taste: the chicks experimented on by Lloyd Morgan, for example, showed disgust on picking up bits of orange peel instead of yolk of egg (506, pp. 40- 41). Herring gulls make similar manifestations on being fed salt fish, and take bread soaked in meat juice more readily than water-soaked bread (697). Raspail (626) thinks that birds abandon eggs which have been handled because they detect the fact by smell; that they find buried grubs by smell, and are guided by this sense to concealed food and water. The last statement he supports by the observation that their tracks lead straight to hidden food on their first visit to it, showing that it was not found by accident. Strong (696) made a careful study of the olfactory apparatus in twenty-seven of the thirty-five existing orders of birds. He concludes that “the olfactory organs of birds are of too great size to be set aside as nonfunctional,’”’ but that as one passes from the lower to the higher orders of birds there is a tendency towards retrogression in these organs. The crow family, sometimes considered to be the highest birds, show extremely minute smell organs. ‘“‘The sense of smell has evidently been disappearing in birds with the great development of vision.”

_smell may somehow function in guiding the long flights of birds. Watson (770) found that the noddy tern could find its way from Key West to its nest on the Tortugas with the nostrils tightly sealed. Strong, however, points out that this bird has very small olfactory organs, and thinks it possible that other birds may make more use of the olfactory sense in homing and migrations. The fulmar, for instance, is a bird which makes very long ocean flights, and has an enormously developed olfactory apparatus. Strong (696) made experiments with the ring dove in which he was apparently able to establish some association between the smell of bergamot in a certain compartment and the choice of that compartment as containing food.

When we come to the Mammalia, we find in the great majority of types a very high development of qualitative discrimination in the sense of smell. Hunters know it to be the chief defensive weapon of wild animals, and it has retained great keenness in many domesticated ones, — the cat, for instance, which will be awakened from slumber in the garret by the odor, quite unsuspected of human nostrils, of some favorite food being prepared in the kitchen, and is thrown into ecstasy at a faint whiff of catnip. The dog, however, is the hero of this field of mental prowess. The experiments of Romanes on the power of a favorite setter to track his scent are well known. In one of them he collected a number of men, and told them to walk in Indian file, ‘each man taking care to place his feet in the footprints of his predecessor. In this procession, numbering twelve in all,” Romanes says, ‘“‘I took the lead, while the gamekeeper brought up the rear. When we had walked two hundred yards, I turned to the right, followed by five of

the men; and at the point where I had turned to the right, the seventh man turned to the left, followed by all the remainder. The two parties ... having walked in opposite directions for a considerable distance, concealed themselves, and the bitch was put upon the common track of the whole party before the point of divergence. Following this common track with rapidity, she at first overshot the point of divergence, but quickly recovering it, without any hesitation chose the track which turned to the right.”” It had previously been ascertained that she would not follow the scent of any other man in the party save her master, and failing him, the gamekeeper. “Yet... my footprints,’ continued Romanes, “in the common track were overlaid by eleven others, and in the track to the right by five others. Moreover, as it was the gamekeeper who brought up the rear, and as in the absence of my trail she would always follow his, the fact of his scent being, so to speak, uppermost in the series, was shown in no way to disconcert the animal following another familiar scent lowermost in the series” (644). Such behavior indicates not only that the dog can experience a variety of smell qualities, which is also the case with us human beings, but that it has the power to analyze a fusion of different odors and attend exclusively to one component, a power that we lack almost entirely. When we experience two smell stimuli at the same time, it is but rarely that we can detect both of the two qualities in the mixture; usually one of them swamps the other, or else a new odor unlike both results. But the dog, and probably many other animals, can analyze a smell fusion as a trained musician analyzes a chord. In this respect, if not in the variety of smell qualities, the olfactory sense has undergone degeneration in us, and so far as we can judge, the fact is due to the habit

of relying rather upon the sense of sight. Even in the case of the monkey, Kinnaman reports that the animals he was testing with regard to their power of discriminating the size, shape, and color of vessels in one of which food was placed, always looked, never smelled, for the food (401). THE sense of hearing, in all air-dwelling animals, is that sense whose adequate stimulus consists in air vibrations ; for human beings these vibrations may reach a frequency of 50,000 (single vibrations) in one second and still produce an auditory sensation. But the meaning of the term ‘“‘hear- - ing” for water-dwelling animals, and hence for most of the lowest forms of animal life, is more difficult to determine.

“Tn the Protozoa it seems to have no meaning at all; the reactions of these animals to water vibrations are indistinguishable from their reactions to mechanical stimulation. But in some of the ccelenterates the possibility of a specific auditory sensation quality has been suggested by the discovery of a peculiar sense organ. While varying in its structure in different genera and orders of ccelenterate animals, this organ consists typically of a small sac, filled with fluid and containing one or more mineral bodies. ~~ Rpparently these latter could operate in connection with a stimulus only when the stimulus was constituted by shaking the animal, Orin some way disturbing its equilibrium. They might eves means for the reception of water vibrations, as the ear serves for the reception of air vibrations; they might, in short, be primitive organs of hearing. Accordingly the term “‘otocysts” was given to organs | of this type wherever they were found in the animal

kingdom, and the mineral bodies in the otocysts were called otoliths. But experiments upon ccelenterates have-entirely failed to show that animals of this class react to sounds (205, 741, 521). And in some ccelenterates, as well as in higher animals having the same type of organ, the removal of the so-called otocysts has been found to involve disturbance of the animal’s power to keep its balance and maintain a normal position. Hence Verworn has suggested that for “otocyst” and “otolith” the terms ‘‘statocyst” and “‘statolith” might appropriately be substituted (741). In jellyfish, indeed, even the balancing function of the statocyst organs appears doubtful; and it is possible that they function in response to shaking and jarring (514, 521). In any case, there is no evidence whatever of a specific auditory sensation in the consciousness, if such exists, of coelenterate animals.

Nor has any reaction to sound been demonstrated in either the flatworms or the annelid worms; their sensitiveness to vibrations seems to be an affair of mechanical stimulation. Darwin’s experiments on this point are well known. The earthworms which he observed were quite insensitive to musical tones, but when the flower pots containing their burrows were placed on a piano, the worms retreated hastily as soon as a note was struck (171). Most observers agree that mollusks also react only to mechanical jars (e.g., 190), and that the statocyst organs found in some mollusks have no auditory function. Bateson, however, records that a. certain lamellibranch, suspended by a thread in a tank, re- ' sponded by shutting its shell when a sound was produced by rubbing a finger along the glass side of the tank (25). The echinoderms are apparently insensitive to auditory stimuli (617, 641).

Tn the Crustacea the function of the statocyst organs has been the subject of much dispute. They are in this group of animals sometimes closed sacs with statoliths, sometimes open sacs containing grains of sand. Most commonly the organs are situated in the basal segment of the small antenne. There is usually inside the sac a projection bearing several ridges of hairs, graded in size, which tempt to the hypothesis that they respond to vibrations of different wave lengths, as the fibres of the basilar membrane of the human cochlea are supposed by the Helmholz theory to do. Hensen, indeed, placing under the microscope the tail of a small shrimp, Mysis, whose statocyst is situated in that region, observed that the long hairs of the tail vibrated in response to musical tones, from which he infers that the statocyst hairs may do so! (294). In 1899 he was still inclined to believe that the latter can serve no other than an auditory function (295). Nevertheless the weight of authority is in favor of regarding the “sac” in Crustacea as a static rather than an auditory organ. The only evidence of sound reaction in two shrimplike forms, Palemon and Palemonetes, was a ‘‘flight reflex” given by some individuals when sounds were produced very near them in the water; and although this response ceased when the statocysts were destroyed, the fact is of little significance, as other reflexes also were abolished by the operation (38). To sounds made by tapping the wall of the aquarium Palemonetes reacted by leaping away from the wall nearest to it, even though the leap was made toward the

1 This observation is sometimes incorrectly quoted as if the hairs concerned were actually the statocyst hairs. Cf., for example, Morgan, 504, p. 266. sound. When both statocysts were removed, the reactions were still made, but not so markedly nor at so great a distance from the sound. A similar response to the striking of a partially submerged glass jar was seen in a decapod, Virbius zostericola, which has no statoliths (616). Mysis has been found to react to sounds when the statocysts are destroyed (48). The fiddler crab, which is amphibious, responds in water to vibrations by retreating slowly from the vibrating walls, and does the same when blinded and deprived of its statocysts, but gives no reaction when the antenne and antennules are removed. On land these animals do not respond to sounds, only to vibrations produced in the earth, for instance by stamping (616). No sound reactions have been found in the crayfish (40). In short, such responses to vibrations as occur among the Crustacea seem affairs rather of mechanical than of true auditory stimulation; nevertheless Bethe (48) and Hensen (295) are both inclined to believe, as did Delage, who first called attention to the static function of the statocysts (180), that they may be auditory organs also. The “‘static sense” of Crustacea will be discussed later.

In spiders the same difficulty arises, of deciding whether the.reactions to sound are tactile or auditory. There are no statocysts, but the delicate hairs on the body and legs of the animal have been held to be auditory organs. Dahl, a number of years ago, found them responding to the tones of a violin (166, 167), but this test, which Hensen applied to Mysis, is of very doubtful significance; as Prentiss suggests, the hairs on the back of the human hand do the same (616). When various species of spiders were tested by holding

tuning forks near them or their webs, only the web-making species gave any response. These latter would not react to ordinary noises, nor to the sound of a small fork, but to the humming of a large fork they responded always by raising the front legs, and sometimes by dropping from their webs (570). Two Texan species that were experimented upon by placing them in a cage free from vibration gave no response whatever to tuning forks of various pitches or to other sounds (618). ({t seems, then, highly probable that spiders are sensitive only to vibrations communicated to their webs, and very likely these furnish tactile rather than specific auditory stimulation) The observation of Boys / may be quoted: ‘On sounding an A fork, and lightly touching with it any leaf or other support of the web or any portion of the web itself, I found that the spider, if at the centre of the web, rapidly slews around so as to face the direction of the fork, feeling with its fore feet along which radial thread the vibration travels. Having become satisfied on this point, it next darts along that thread till it reaches either the fork itself or a junction of two or more threads, the right one of which it instantly determines as before. If the fork is not removed when the spider has arrived it seems to have the same charm as any fly, for the spider seizes it, embraces it, and runs about on the legs of the fork as often as it is made to sound, never seeming to learn by experience that other things may buzz besides its natural food. If the spider is not at the centre of the web at the time that the fork is applied, it cannot tell which way to go until it has been to the centre to ascertain which radial thread is vibrating.” If, however, it has followed the fork to the edge of the web, and the fork is then withdrawn and brought near again, the spider reaches out in its direction.

If the spider is at the centre of the web and a sounding fork is brought near without touching the web, the spider does not reach for it, but drops down at the end of a thread. If the fork touches the web again, the spider climbs the thread and finds the spot very quickly (100). The sense of hearing in insects also is problematical. When the insect makes a sound itself, which, -as in the case of crickets, is connected with the mating process, it would seem a priori highly probable that it can hear. (Various structures have been designated as auditory organs, the finely branched antenne of mosquitos and gnats, on the same . doubtful evidence that they have been found to vibrate in response to musical tones (479); and in the Orthoptera certain very peculiar structures situated on the front legs of grasshoppers and crickets, and in the first segment of the abdomen in locusts.) These structures Graber called chordotonal organs, and he felt convinced from experimental tests that they were auditory.) The cockroach, Blatta, while running about the room will stop, he says, for an instant when the strings of a violin are struck. A blinded specimen, hung by a thread, became violently agitated at a sudden tone from a violin. A water insect, Corixa, although undisturbed by the water vibrations produced by pushing a bone disk toward it in the water, gave decided reactions when the disk was connected with an electric bell. Other water beetles were still more sensitive. That they distinguished pitch differences Graber thought probable from the fact that he observed reactions of different degrees of violence to sounds of different pitch; and their discrimination of intensity changes he thought demonstrated by the fact that if a continuous tone, sounding while a water

beetle is swimming about, be made suddenly louder, the speed of the insect’s movements visibly increases. It is going rather far, however, to pass from the evidence that insects discriminate sounds made by their own species from other sounds to the conclusion that “they like us have the capacity to analyze, at least to a certain degree, these peculiar clangs or noises, and to distinguish clearly from one another the partial tones that compose them” (264).

Tower thought that he had observed the potato beetle reacting to the sound of a tuning fork (717). Will noted responses from a male beetle to the stridulation of a female of its species enclosed in a box 15 cm. away (786). RAdl made the suggestion that the organs which Graber called chordotonal organs, and which contain a fibre stretched between two points of the integument, represent a kind of transition between ‘“‘Gemeingefuhl” and hearing) In support he offers the following evidence: the fibres resemble the tendons in which some muscles end, and are very likely developed from tendons; the organs exist in insects that have no use for hearing, such as grubs shut up in fruits ; insects have not been shown to respond to pure tones, but only to noises, such as the cricket’s chirping, which for us affect Gemeingefuhl. Further, (there is no evidence that hearing ever guides insects to each other; in short, it is but a rudimentary sense, and its organs are those which serve also to register muscular activity. It is, in insects, a “refined muscular sense’ (624). Regen (630) demonstrated very prettily an apparently auditory reaction in the female cricket. He placed in the centre of a wide area on the floor two glass vessels, one lined with black paper, the other transparent. In the opaque vessel he placed a chirping male; in the transparent vessel a quiet male.

Normal females ran to the vessel which contained the chirping male, but ignored the other vessel: females whose “tympanal organs’ on the forelegs had been operated on did not react to either vessel. That the response was not to an odor liberated by the movement of the male’s wings in chirping, was shown by removing the edges of the wings, so that their motion, while otherwise unchanged, was noiseless: the response of the females ceased. (It seems likely that the auditory sense, if it exists in insects, would be confined to those which produce sounds) and its qualities limited within the range of such sounds) Turner (731), however, finds that silkworm moths, alighted on hanging shelves and thus protected from jarring, respond by waving their wings when an organ pipe, a pitch pipe, and various notes on the Galton whistle are sounded. One species, which failed to respond, he rendered more excitable by rough handling, and then succeeded in stimulating the sound reactions. Several different species of Catocalo moths were found to respond to high notes on the Galton whistle, either by flying or by quivering their wings. By touching the insect at the moment when the tone was sounded, thus giving it a “‘life significance” to the insect, some of the moths were trained to react to a lower organ tone (256 vibrations) even when they were not touched. These moths are not known to make sounds (733). Most species of ants produce no sound that the human ear, even with the aid of a microphone (441), can detect, although certain East Indian species are reported to make a loud hissing noise when disturbed (760), and some American species are said to chirp (202, 782). Ch. Janet maintains that ants of the Myrmicide make a stridulating noise (357, 358). The weight of evidence

is also against the existence of sound reactions in ants ;) careful experiments by Fielde and Parker on a number of species led to the conclusion that the only vibrations responded to were those which were communicated through the solid on which the ants stood, and received through the legs (226). It is probable that the observers who have come to opposite conclusions have not in every case been careful to exclude the possibility of such vibration of the substratum. Wasmann, for instance, thinks he has seen reactions to sound; he noted that ants in an artificial nest raised their antenne and lifted the fore part of their bodies when he scratched with a needle on some sealing wax with which the nest had been mended (759). He also quotes Forel’s account (230) of a species which makes an “alarm signal” by striking the ground with its abdomen: this, remarks Wasmann naively, must be perceived by the ants, ‘otherwise it would not be an alarm signal”! (760). If perceived, it may of course be as a tactile rather than an auditory sensation. eld has observed reactions to the sound of whistles and tuning forks in several species of ants, and even concludes that they perceive the direction from which sounds come; but since, of the four observations upon which this latter opinion is based, two were cases where the ants hurried toward the sound and the others cases where they backed away from it, the possibility of mere coincidence seems not to be excluded (776).

\As regards the auditory sense in bees, there is again a difference of opinion} They do, of course, make sounds, and sounds of different quality, under different conditions. Yet Lubbock entirely failed to get bees to respond to any kind of sounds artificially produced (441), white Bethe urges - that the sounds produced by bees are involuntary, like the sounds of our own breathing and heart-beats, and that there is no more evidence that bees can hear them than that we can hear these sounds in our own case (52). Forel is positive that insects in general cannot hear (231). Von Buttel-Reepen, on the other hand, who knows bees thoroughly, thinks that the sense of hearing plays a considerable part in their life. He believes that the disturbance produced by the loss of a queen is communicated to the whole hive by the peculiar wailing noise made by some members and instinctively imitated by the others, and that this disturbance is calmed by a similar dissemination of the “happy humming”’ produced on her restoration — hearing playing a more important part than smell. The starting of a swarm, he thinks, is also largely a matter of sound communication. The process begins by the coming out of certain bees which push in among the bees hanging at the entrance of the hive and stir them up to swarming by making sounds. The “swarm-tone” is peculiar and often disturbs the inhabitants of neighboring hives that are not ready to swarm. Also, a swarm can be guided to a new dwelling if a few bees are taken there; they call the others by loud humming. If during this process the new hive is moved, the bees will go on for a few moments: in the direction in which they started, then slowly turn, guided by the tone. A few may keep on in the original direction. We may look with suspicion, however, upon von Buttel- Reepen’s suggestion that these latter, having passed beyond hearing of the call, are guided by the recollection of the tone they heard at first! He refers also to the shrill noise made by the young queens ready to swarm, and to the peculiar uneasiness produced when a strange queen is being attacked, and resulting, he thinks, from her ‘‘cries of pain” (115).

Throughout the vertebrate animals there exist structures bearing analogy to our own ears, whose function might therefore be supposed to be auditory. (But in the lowest vertebrates the only structures of the human ear represented are the semicircular canals, and these suggest a static rather than eae. The cyclostomes, eel-like and semiparasitic forms classed below the true fishes, have a pair of sacs one on either side of the head, containing mineral bodies, and each leading into one or two semicircular canals. In the true fishes the sac has two Chambers, marked off from each other by a constriction. Three semicircular canals open from the foremost chamber, two lying in the vertical plane, and one in the horizontal plane. The chambers contain ‘‘statoliths’’ and fluid.