Augtisi 21, 1879] 



NATURE 



395 



India. What are more emphatically old world forms than the 

 camel, horse, and elephant, with the typical porcupine? Yet 

 all these existed in America in Pliocene times. Did we know 

 the Tapir in only one of the two widely-separated stations in 

 vhich it dwells to-day, we might well deem its evolution to be 

 due to migration and isolation. But we know from palaeon- 

 tology that It existed in Europe from the Eocene to the Pliocene 

 period. 



Such facts as these do not, of course, disprove the doctrine 

 that migi-ation and isolation are necessary antecedent conditions 

 to specific genesis, but they show how much caution must be 

 used in drawing the conclusion that they are necessary, from the 

 distribution of animals much less likely to be found fossil than 

 mammals are. 



But an argument in favour of the views of Buffon and of 

 Wagner may be obtained from our o^vn species, which exhibits 

 some singular coincidences between peculiarity of form and iso- 

 lation. Among such instances may be mentioned the Tasma- 

 nians, the Andaman Islanders, and the Ainos or Aborigines of 

 Japan. One of the most striking examples is that of the Eskimo 

 — a people representing many peculiarities, some of which ex- 

 aggerate the characters of the highest races of mankind. Thus, 

 the pelvis differs from the European pelvis in an opposite direc- 

 tion to that by which the negro pelvis differs from the European, 

 and the same is the case with the proportions of the limbs, while 

 the skulls of the Eskimo have the largest and narrowest nasal 

 aperture of all races, being in this respect the very opposite to 

 the Australians. The Eskimo have migrated eastwards, not 

 reaching the south of Greenland till the fourteenth century, and 

 the race characters are most marked in the most easterly tribes. 

 These facts were brought forward by Prof. Flower in his Hun- 

 terian lectures for the present year,^ when he said that the cha- 

 racters of this peculiar race ' ' must be attributed to those gradual 

 modifications produced by causes at present little understood, by 

 which most of the striking variations met with in the human 

 species have been brought about — modifications more strongly 

 expressed the more completely isolated the race has become, and 

 the farther removed from its original centre of distribution." I 

 think, then, that though we have not data for conclusively 

 answering the question as to how far migration (together with 

 isolation) may be necessary for specific genesis, it is certain that 

 it is of very great efficacy and importance, and that credit is 

 justly due to Buffon for his early appreciation of its importance. 



The next question to which I would advert is that concerning 



THE DIRECT ACTION UPON ORGANISMS, OF THE EXTERNAL 

 CONDITIONS WHICH SURROUND THEM. 



Buffon's belief was ^ that changes of specific form were brought 

 about by change of temperature and_^climatic change generally, 

 as well as by change of food. 



The curious effects of stimulating food on colour — as of 

 cayenne pepper with canaries, and hemp-seed withjparrots — is 

 notorious. 



The direct action of the environment on organisms has, I 

 think, been of late somewhat undervalued. Amongst evidences 

 in favour of its importance, I would refer to some of Mr. Alfred 

 \VaUace's observations.' He tells us that in the small island of 

 Amboina, the butterflies (twelve species of nine different genera) 

 are larger than those of any of the more considerable islands 

 about it, and that this is an effect plainly due to some local in- 

 tluence. In Celebes, a whole series of butterflies are not only 

 of a larger size, but have the same peculiar form of wing. The 

 iJuke of York's Island seems, he tell us, to have a tendency to 

 make birds and insects white or at least pale, and the Philip- 

 IJincs, to develop metallic colours, while the Moluccas and New 

 Guinea seem to favour blackness and redness in parrots and 

 pigeons. Species of butterflies which in India are provided 

 with a tail to the wing, begin to lose that appendage in the 

 islands, and retain no trace of it on the borders of the Pacific. 

 The /lincas group of Papilios never have tails in the equatorial 

 region of the Amazon Valley, but gradually acquire tails, in 

 many cases, as they range towards the northern and southern 

 tropics. Mr. Gould says that birds are more highly coloured 

 under a clear atmosphere than in islands or on coasts — a condi- 

 tion which also seems to affect insects, while it is notorious that 



* The lecturer also said ; " The large siie of the brain of all the h>*per- 

 borean races. Lapps as well as Eskimo, seems not necessarily to be con- 

 nected with intellectual development, but may have some other explanation 

 not at present apparent." I would suggest that in this case — as in the large 

 brains of Cetaceans — it may be due to the need in their climate of generat- 

 ing much heat to sustain the necessary temperature of the body. 



Of. cit., vol. xiv. p. 317. 3 bee ** Tropical Nature," pp. 254-259. 



many shore plants have fleshy leaves. I need but refer to the 

 English oysters mentioned by Costa, which, when transported-; 

 to the Mediterranean, grew rapidly like the true Mediterranean 

 oyster, and to the twenty different kinds of American trees, said 

 by Meehan to differ in the same manner from their nearest 

 European allies, as well as to the dogs, cats, and rabbits which 

 have been proved to undergo modifications directly induced by- 

 climatic change. 



It appears, then, that much may be said in favour of that 

 direct effect of surrounding circumstances on organisms in which 

 Buffon believed. 



Lastly, I would refer to Buffon's belief that new species have- 

 arisen by DEGRADATION. This again is an opinion which, after 

 a period of disfavour, or at least of neglect, has been of late 

 revived, and has acquired considerable influence. I may here 

 refer to Anton Dohrn, who has recently advocated the very 

 widely-spread and effective action of degradation as a cause of 

 specific change. It will, I think, be generally admitted that 

 such exceptional Copepod crustaceans as Tracheliastes and Ler- 

 ncocera are due to degradation, and the probability seems to me 

 very strong that the Rhizocephala, at least many cirripeds, anci 

 the certoid worms, are also degraded organisms. Very interest- 

 ing would it be to know whether existing Ascidians are also ex- 

 amples of degradation, as not a few zoologists now suppose ;. 

 but most interesting of all is that parasite of cuttle fishes, 

 Dicyema, the stracture of which has been recently investigated 

 by Prof. Eduard van Beneden, and made the type of a new 

 primary division of animals. Should this small worm-like or- 

 ganism hereafter turn out to be a degraded form, it will shov^ 

 what an extreme degree of retrograde metamorphosis may occa- 

 sionally be brought about. I think, then, that we have con- 

 siderable ground for suspecting that degradation has acted much 

 and widely in the field of Biology, and if so, Buffon is fairly 

 entitled to a certain amount of esteem on account of the views 

 he entertained with regard to it in so early a day and in so un- 

 developed a condition of zoological science. For it must not be 

 forgotten that migration, the influence of external conditions, - 

 and degradation, are connected points : parts of one view. De- 

 gradation is most conspicuous under violent changes of condition 

 (such as parasitism), while migration only acts by bringing orga- 

 nisms under new conditions. 



These reflections lead me to urge upon such of my hearers as 

 may have any unusual facilities for experimental investigation, a 

 course of inquiry which seems to be very desirable. 



What is needed in order to solve as far as possible the ques- 

 tion of specific genesis, is a knowledge of the laws of variation,, 

 which must, I think, be deemed the true cause and origin of 

 species. 



We may, I think, accept as true two propositions : — 



1. Animals may change in various ways, and amongst them,, 

 by degradation. 



2. Changes in the environment with isolation, induce and ■■ 

 favour changes in form. 



I would urge, then, that inquu-ies should be pursued in two 

 directions simultaneously. 



A. There might be undertaken one set of inquiries to investi- 

 gate the effects on different species of the same variations of 

 environment. 



B. Other inquiries might be undertaken with a view to ascer- 

 taining the effects of different changes of environment on one 

 and the same species. By series of experiments contrived with 

 these ends in view, and carried on with various selected animals 

 and plants which reproduce with rapidity, we may possibly be 

 able to determine what to attribute to external influences (shown 

 by such influence having the same effects on all), and what to 

 the peculiar nature and innate powers and tendencies of different^ 

 organisms — shown by the diverging reactions of the latter under 

 the same changes in their environment. 



I next desire to direct your attention to another matter treated- 



of by Buffon — I mean THE RESEMBLANCES AND DIKFERENCES 

 WHICH EXIST BETWEEN THE MIND OF MAN AND THE HIGHER. 

 PSYCHICAL FACULTIES OF ANIMALS. 



This question is eminently a question of our own day, and 

 one which I feel cannot but excite interest in this section. 



But its accurate investigation is attended with special diflicul- 

 culties, and amongst them are two temptations, which are apt to- 

 beset the inquirer ; 



1. The first of these arises from the wide-spread lore for the 

 marvellous of whatsoever kind, and |the tendency to inverted 

 anthropomorphism. 



