Materials for the Study of Variation Treated with Especial Regard to Discontinuity in the Origin of Species

It is needless to call attention to the fact that in hardly any cases even of extreme variat ions in wild creatures is there evidence that the animal wa^ unhealt hy, »r ill nourished, or that its economy was in any visible way upset ; but in almost every example, save for the variation, the body had the appearance of normal health. A tier all that has been said few perhaps will still ask us to believe that the fixity of a character is a measure of it> importance to the organism. To try to apply such a doctrine in the open air of Nature leads to absurdity. Let one more case be enough. I go into the fields of the North of Kent in early August and I sweep the Ladybirds off the thistles and nettles of waste places. Hundreds, sometimes thousands, may be taken in a few hours. They are mo>tly of two species, the small Cocdnella decempunctata or i'iiri(ilii/in and the larger C. septempunctata . Both are exceedingly common, feeding on Aphides on the same plants in the same places at the same time. The former (C. decempunctata) shews an excessive variation both in colours and in pattern of colours, redbrown, yellow-brown, orange, red, yellowish-white and black, in countless shade>, mottled or dotted upon each other in various ways. The colours of pigeons or of cattle are scarcely more variable. Yet the colour of the larger C. septein/xaictatu is almost absolutdy conMant. having the >ame black spots on the same red ground. The slightest difference in the size of the black spots is all the variation to be seen. (It has not even that dark form in which the blac"k spreads over the elytra until only two red spots remain, which is to be seen in C. l>ij>iuirt</t<i.) To be asked to believe that the colour of C. septempunctata is constant because it matters to the species, and that the colour of C. decempunctata is variable because it does not matter, is to be asked to abrogate reason.

But the significance of the facts does not stop here. When, looking further into the variations of (.'. decempunctata it is found that most of its innumerable .shades of variation are capable of being grouped round some eight or ten fairly distinct types, surely an expectation is created in the mind that the distinctness of these forms of varieties, all living [and probably breeding] together, may be of the same nature as the distinctness of Species ; and since it is clear that the distinctness of the varieties is not the work of separate Selection we cannot avoid the suspicion that the same may be true of the specific differences too.

An error more far-reaching and mischievous is the doctrine that a new variation must immediately be swamped, if I may use the term that authors have thought fit to employ. This doctrine would come with more force were it the fact that as a matter of experience the offspring of two varieties, or of variety and normal, does usually present a mean between the characters of its parents. Such a simple result is, I believe, rarely found among the facts of inheritance. It is true that with regard to this part of the problem there is as yet little solid evidence to which we may appeal, but in so far as common knowledge is a guide, the balance of experience is, I believe, the other way. Though it is obvious that there are certain classes of characters that are often evenly blended in the offspring, it is equally certain that there are others that are not.

In all this we are still able only to quote case against case. No one has found general expressions differentiating the two classes of characters, nor is it easy to point to any one character that uniformly follows either rule. Perhaps we are justified in the impression that among characters which blend or may blend evenly, are especially certain quantitative characters, such as stature; while characters depending upon differences of number, or upon qualitative differences, as for example colour, are more often alternative in their inheritance. But even this is very imperfectly true, and as appeared in. the case of Earwigs (p. 40) there may be a definite dimorphism in respect of a character which to our eye is simply quantitative. Nevertheless it may be remembered that it is especially by differences of number and by qualitative differences that species are commonly distinguished. Specific differences are less often quantitative only.

But however this may be, whatever may be the meaning of alternative inheritance and the physical facts from which it results, and though it may not be possible to find general expressions to distinguish characters so inherited from characters that may blend, it is quite certain that the distinctness and Discontinuity of many characters is in some unknown way a part of their nature, and is not directly dependent upon Natural Selection at all. The belief that all distinctness is due to Natural Selection, and the expectation that apart from Natural Selection there would be a general level of confusion, agrees ill with the facts of Variation. We may doubt indeed whether the ideas associated with that flower of speech, " Panmixia," are not as false to the laws of life as the word to the laws of language.

But beyond general impression, in this, the most fascinating part of the whole problem, there is still no guide. The only way in which we may hope to get at the truth is by the organization of -ystematic experiments in breeding, a class of research that calls perhaps for more patience and more resources than any other form of biological inquiry. Sooner or later .such investigation will be undertaken and then we shall begin to know. Meanwhile, much may be done to further the Study of Variation even by those \\ho have none of the paraphernalia of modern science at command. Many of the problems of Variation are pre- • •niineiit ly suited for investigation by simple means. If we are to get further with these problems it will be done, I take it, chiefly by -tudy of the common forms of life. There is no common shell or butterfly of whose variations something would not be learnt were some hundreds of the same species collected from a few places and statistically examined in respect of some varying character. Anyone can take part in this class of work, though fewr do.

At the present time those who are in contact with the facts and material necessary for this study care little for the problem, or at least rarely make it the first of their aims, and on the other hand those who care most for the problem have hoped to solve it in another way. These things attract men of two classes, in tastes and tempera ment distinct, each having little sympathy or even acquaintance with the work of the other. Those of the one class have felt the attraction of the problem. It is the challenge of Nature that calls them to work. But disgusted with the superficiality of "naturalists" they sit down in the laboratory to the solution of the problem, hoping that the closer they look the more truly will they see. For the living things out of doors, they care little. Such work to them is all vague. With the other class it is the living thing that attracts, not the problem. To them the methods of the first school are frigid and narrow. Ignorant of the skill and of the accurate, final knowledge that the other school has bit by bit achieved, achievements that are the real glory of the method, the "naturalists" hear onlv those theoretical conclusions which the

Laboratories from time to time ask them to accept. With senses quickened by the range and fresh air of their own work they feel keenly how crude and inadequate are these poor generalities, and for what a small and conventional world they are devised. Disappointed with the results they condemn the methods of the others, knowing nothing of their real strength. So it happens that for them the study of the problems of life and of Species becomes associated with crudity and meanness of scope. Beginning as naturalists they end as collectors, despairing of the problem, turning for relief to the tangible business of classification, accounting themselves happy if they can keep their species apart, caring

little how they became so, and rarely telling us how they may be brought together. Thus each class misses that which in the other is good. But when once it is seen that, whatever be the truth as to the modes of Evolution, it is by the Study of Variation alone that the problem can be attacked, and that to this study both classes of observation must equally contribute, there is once more a place for both crafts side by side : for though many things spoken of in the course of this work are matters of doubt or of controversy, of this one thing there is no doubt, that if the problem of Species is to be solved at all it must be by the Study of Variation.

Afiiiithuilrilii*, double tail, 50.1 Ai;tntlii>tlii/ri.<. double monster, 50ii Acce-sory hoofs of Ox, connected with supernumerary dibits. 'Js'i Ai-li,-r<iiitiii atropos, colours of larva.- . Hill. Adaptation, Study of, as a method of problems of species. Id; objection to the metbod, 12: species, approximate only, 11 Aiiiiiinniii tuiiiii-iti, double (?) antenna, partial duplicity of a ray. 4 Hi Aiiintiifii'tca, alleged case of eight pairs not in multiples of five. 435 Aiiijiliiiiuilln.i milntitiiili*, extra autenn.-i .

Annelids, segmentation compared with that of Chordata, Hi;: imperfect segmentation, 15(5; spiral segmentation, supposed double, 548 Anthia, extra legs, 502 Anthocharis cardamines, colour-variation. 4"> Ai-tliroiitniKiltix. number of segments, 94 Arthropoda, variation in number of segments, 87; Homo-osis in appendages, llti; axial duplicity, 565 Articular processes, change from dorsal to lumbar type, 109; variations in position of change, 110, 112, 114, 117,

dactylism, 383 ; teeth, 245, 246 Ascidin plebcia, specimens having every fourth vessel of branchial sac dilated, of digital variation in, 360 Astaeusftuviatilis, colourvariation, 44 variation in number of oviducal openings, 84, 152 absence of male opening, 154 absence of oviducal A. piliiiKiinis and braziliensis, apparent presence of female opening in males, AaterUm, variation of pedicellarite, 429; in generative organs, 167 Aurelia aiirit/i, Meristic Variation of,

Baer, von, Law of, 8; its proper scope, 9 ; probably not applicable to cases of Discontinuous Meristic Variation, Balanofllossus, two methods of development, 9 ; number of gill-slits, 174 ; extra proboscis-pore, 466 ; supposed relation to Chordata, 86 Bdellostoma, individual and specific variations in number of gill sacs, 173, 174 cirrhatum, heptatrema, hetcrotrema, hexatrema , 173; bischoffi,polytr>ema, Beech, fern-leaved, 25 Bees, hermaphrodite, 68 ; union of eyes, 461 ; antenna modified as foot,

cuniculus, lesueri, penicillata, 258 Bilateral asymmetry, Homceosis in cases Bilateral Symmetry, 19 ; in variation of vertebrae, 128; in variation of Annelids, 167 ; in variation of niamnia?, 183; in variation of teeth, 267 ; in cervical fistulas, 175; in variation of ocelli, 292 ; in variation of digits, 402; in variation in antenna? of Forjicula, 414 ; in variation of Radial Series, 427 ; in abnormal branching of Antedon, 438; in distribution of triasters in segmenting egg, 464 ; in abnormal union of blastomeres, 464 as found in manus and pes,

influence on Secondary Symmetries doubtful, 557 Bipinnaria, extra water-pore, 466 Birds, spinal nerves, 129 ; digital Variation, 390, 396 Blaniulus, mode of increase in number Blaps, extra legs, 512; extra antenna?, attenuata, 522; double antenna, chevrolati, cylindrica, similis, 551 Blatta, variation in number of tarsal joints, discussion of, 63 ; facts, 415 ; regeneration of tarsus with 4 joints, Callidiuiu ruridltilf, double (?) antenna, 5."il ; rialiiffitm, extra antenna aiisiug from head, ^>'ii Calliniorphti, colour-variation of species

Castration, parasitic, of crabs, 95 Cat, variation in colours of, 48 herited, 323 spinal nerves, 138 teeth, 222 vertebrae, 122 Caterpillars, segmental Kepetition of Cebidae, teeth, 205 Cebus, teeth, 205 Cell-division, variations in, 430 Centrosoraes, variations in number of, antenna arising from head, cerdo, 551 Cercocebus, teeth, '204 Cercopithecus, teeth, 204; abnormality Ceroglossus valdivue, extra legs, 500 Cervical vertebra, assumption of dorsal

rtifus, premolar, 246 dauia, extra digits, 379 Cestoda, variation in segmentation of, Chamois, extra horns, 286 clutradritis, brachial plexus, 130, 132 Chelae, extra parts in Secondary Symmetry, 528; amorphous cases, 538; duplicity of, 540 developed from third maxillipede Chelonia, axial duplicity, 563 Cherap* preissii, apparent presence of female openings in males, 155 CliiusoyiHitiins ijrantii, double (?) antenna, 551 Chilognatha and Chilppoda, variation in

Chitons, repetition of eyes in, 26; variation in colours of scutes, 307 Chltcnius nir/ricornit>, extra legs, 512; < 'Imlurnia, hallux absent, 397 Chordata, segmentation of, 86 Chroicocephalux, brachial plexus, 130 Cliri/tscmijn, axial duplicity, 563 Chrysomela, division of pronotum,/«ca ta, Clavatelht, variation in number of segments, 425 ; in number of eyes in each segment, 425 Goccinella decempunetata, bipunctata and xeptempunctata, colour-variation, 4'.l, 572

Colias, colourvariation, 44 ; intermediates between edusa and helice, 44 ; varieties of Injale, 45 Colour-variation, discontinuity of, perhaps chemical, 72 ; simultaneous, in segments, &c., 303 Continuity, use of term as applied to Variation, 15; of differences in En- vironment, 5 Correlation, between variations of nerves and vertebrae, 145 ; between Meristic and Substantive Variation, 126 Crustacea, theory of descent of Vertt - brata from, 29; of salt lake-, lull: Secondary Symmetry in, 525; Hoinceosis in, 149

Ci/;i nun ofor, cervical vertebrae, 33 ; colourvariation of young, 41; atrutnx, brachial plexus. 130 jili<iln* jinrfiiriuf, extra molar, 204 iifs carpiti, bulldog-headed varieties,57; hungaricus, ditto, 58; tinnitus, division of tins, 451 hallux and pollex, 401 Dactylopodites, extra, "r_'s linrti/liijiailii, jn-emolars, 255 Darwin's solution of problem of Species, lntH*, molars, 25H J>i ili'jiliiln I'uplmrliitr, colours of larva-, Inheritance of Variation in, 398 Recapitulation of evidence, 400 Dimorphic condition, its relation to the

monomorphic condition, 37 Dimorphism in Spinal nerves, 138; in position of generative openings in I'lK-lti/drilim, 165, 168; in secondary sexual characters, 38 Diopatra, abnormal repetition, 159 liiacoidea (Echiuid), 4-rayed specimen. in Variation, a possibility, 17; suggestion as to itnature, 6s, ,3i>s in chemical processes, 1 6, in states of matter, 16 of Meristic Variation perhaps mechanical, 70 of Substantive Variation perhaps in part chemical, 71 in the Variation of spinal

Disease, analogy with Variation, 74 Ditonnm tricwpidatus, double (?) antenna, 550 Dorcadion rutipes, extra legs, 512 Dorking Fowl, digital variations, 390 — Duck, no variation in number of digits recorded, 401 ; cases of absence of webs between toes, 401 Duplicity of single members of series not distinct from other modes of addition, 193, 407 of appendages, 406 ; in Arthropoda, 539; in Vertebrata, Dyschirius f/lobulostis, extra legs, 512 Dytitscus majginalis, extra legs, 512

Earthworms, variation of generative organs, 159 ; of segmentation, 157 ; asymmetrical arrangement of generative organs, 160, 161 ; table of arrangement of ovaries, 162; duplicity of head, 565, of tail, 565 Echinodermata, Meristic Variation in, 432; variations of pedicellariae, 429; duplicity, Echinoidea, Meristic Variation of, 441 ; 4-rayed specimens, 441; partial disappearance of a ray, 443 ; partial duplicity of a ray, 446; 6-rayed specimen, 445; pedicellariae, 429; variation in number of genital pores, 446 ; symmetrical reduction of two rays, 443

Echinus sphcera, partial reduction of an iuterambulacrum, 445 Embryology, as a method of investigating problems of Descent, 7 Encrinus, variation in number of radial joints, 421 ; 4-rayed calyces, 436 ; radius bearing only one arm, 438 Entoniscians, alter segmentation of some crabs but not of all, 95 Eye-spots, 288 ; Variation as a whole, 291 ; outer zones first to appear, 291 ; analogy with chemical phenomena, Generative organs of Earthworms, variations in, 159: of Leeches, 165

Gold-fish, simultaneous variation in length of tail and fins, 309: division of anal and caudal fins, 451; "Telescope," 4.33 colour - variation, 45 ; nature of the yellow pigment, 48 extra wing, 283 Ho?mal spines, division of, in Goldfishes, 453 Hair, absence of, in Mouse. HOIM. ceatus, double (?) antenna, 550 Hawthorn, variation of, 569 Hectocotylus, supernumerary, in Elehisjrida, union of tentacles, 461 Helodenna, vertebrae, 123 Helops cicruleus, extra antennae, 523

sulityenniis, extra palpi, 524 Hemiaster; cases in which one ambulacrum wanting, 445 ; two ambulacra reduced, 443 ; duplicity of ambulacra, Hcpialus humuli, males like females in Heptanchus, seven gills, 174 Heredity, objection to use of term, 75; Heteroceplialus, a naked Eodent, 56 Heterogeneity, universal presence of in living things, 18 symmetrically distributed around centres or axes, Heterorhina nif/ntarsia, division of pro- Hexanchus, six gills, 174 Hipparchia tithonus, eye-spots, 293, 294 Hippocampus compared with Phyllu-

between vertebrae, 106-127 ; backward and forward, use of terms, 111; forward in vertebrae, 112; backward in vertebrae, 111 ; in spinal nerves, 144 ; of appendages in Arthropoda, 146 ; in segments of Annelids with respect to genital organs, 162, 163, 167, etc.; in teeth, 272; in bilateral asymmetry, 465; in parts of flowers, 111 Homology between members of Series of Repetitions, 30 individual, not attributed if series is undifferentiated, 32 ; attempt to trace iu mamma?, 191 ; discussed in the case of teeth, 269; in the case of digits, 351, 391, 371, 377; in the case of joints of tarsus of Blutta, 418 ; in the case of radii of Holothurioidea, 433

naked variety, 56 ; teeth, 244. 245 cervical fistulas, 180 simultaneous variation of mane extra digits, 360 ; by development of digit n, by development of digit iv, 367 by development of digits ii and iv, 368 by division of digit in, 369 by intermediate process, 371 principles of, followed in the structure and position of parts in Minor Symmetry, 479 Inca Dogs, a bulldog found amongst, 57 : \aiiatiun of premolars and molars, Individuality, attributed to members of M eristic Series, 31: such individuality not respected in Variation, 82 ; cases illustrating the absence of supposed individuality in Members of Meristic Srrk-s, 104,' 115, 124, 191, 269, 407, 433; an unfortunate term, 550

by absence of hallux, 390 Jackal, vertebra', 122; teeth, 217 Japanese pug, probable independent Jaws, relation of upper to lower, 190 Jiilnilis cequinoctialis, extra leg>, 503; cloud, double (?) antenna, 551 C/H/MX trrrextris, mode of increase in Kuryoxinesis, symmetry in, 20; variations in, 430; bilaterally symmetrical variation of, in the segmentation of an e;.'i-r, 4i',4 Lamellibranchs, sinistral, 54 Latnin fi'.rtur, double (?) antenna, 551 Liirtix Ictifiijiti-rii*, digit-, 393 Larvae of Lepidoptera, variations in

Leaf-butterfly, colour-variation, 53 Leeches, variation in generative organs Lichiuinthe nilpina, extra antennae, 517 Liyula, absence of segmentation in, 10s Limax, union of tentacles, 400 Liiiti'uitix iKijntli, extra wing, 283 Limiting, division of caudal spine, 450, Line kid mitltijlnrn, fission, 433 Linear Series, Meristic Variation in, 03; simultaneity in colourvariations of, 303 I.ix.-iutriton, supposed double limb, 539 LitlmbiitK, number of segments, 93 I, it IK nit:* urcticti. extra legs, 527 l.itturiiin nulia. colourvariation, 49 l.itturiiid, sp., extra eye, 280 Li.riiK ti>i<ni*t<itiix, division of prouoturn,