December 24, 1891] 



NA TURE 



75 



only its first pair of legs are black and yellow, and these alone 

 are stretched out conspicuously (see Fig. 2). The great dif- 

 ferences between the altitudes of these two closely related 

 moihs, corresponding to the distribution of startling colours 

 upon them, afford a very strong support to the theory of warning 

 colours. Mr. Beddard might reply that they thus make pro- 

 minent the unpalatable pigments that the enemies may first 



make trial of them upon a material which will ensure their 

 ultimate rejection. But if the colour has not a meaning as such, 

 there is no reason why this spot should be attacked in pre- 

 ference to any other part of the exposed surface ; and the 

 existence of the colour as a covering to the most vital parts 

 seems to indicate that it acts as a warning away rather than in 

 the reverse manner. 



The lact that brightly coloured animals are frequently attacked 

 does not seem to me to be a great difficulty. The really im- 

 portant point is whether the enemy remembers the attack, and 

 is assisted in identifying the unpalatable species by its bright 

 colours. Many experiments seem to show that this is so. 

 Ceitainly Mr. Beddard will not assert that the majority of 

 inseci-eating animals fail to know and recognize a wasp without 

 tasting it. Again, the question is really, as Mr. Titchener 

 implies in his interes'ing communication, oneof "comparative 

 palatability " ; and there is no doubt that insect eating animals 

 when sufficiently hungry will attack and sometimes devour 

 insects Ahich they would ordinarily reject. Furthermore, an 

 animal which naturally prefers a varied insect food, and which 

 is fed m c nfinement largely on other substances and partially 

 on a monotonous insect diet, may be expected to be less scrupu- 

 lous than it would be in the wild state. I may state, however, 

 that the most intelligent insect-eating animals, such as the 

 marmo et, hardly ever make mistakes ; their suspicion being at 

 once aroused by any trace of a warning colour. 



It is well known that we chiefly owe the theory of warning 

 colours to Mr. A. R. Wallace. My own conviction of its 

 entire validity rests upon the results of a prolonged series of 

 experimems, of which only a part has been published. I believe 

 that I conduced these experiments fairly, that my mind was 

 open, and that I had no personal bias in the matter at all, 

 either in favour of or against the theory. And I can confidently 

 make the same claim on behalf of others who have experimented 

 in the same manner — such as Mr. Jenner Weir, Prof. Weis- 

 mann, and M. Portchinsky. I may allude especially to the 

 writings of the last-named authority, as they are the most im- 

 portant as well as the most recent contribution to the theory 

 which we owe to Mr. Wallace. 



1 may also take this opportunity of replying to a very similar 

 objection raised by some reviewers against my book on the 

 "Colours of Animals, their Meaning and Use, &c." They 

 point out that I have not alluded to Elmer's work on the com- 

 pari.-,on of ihe wing markings of Papilionidie, and they assume 

 that his paper has, therefore, escaped my attention. But 

 Eimer's paper has no bearing whatever on the value of colour 

 in the struggle for existence, and this is the subject of my book, 

 as anyone can infer from the preface, or even from the title. 

 For this reason I was also compelled to omit reference to what 

 I venture to regard as the far more important work of Weis- 

 mann on the development of the colours and marking of 

 caterpillars, and of Dixey on the wing-markings of Vanessidd: 

 and Ari;ynnid(t, as well as a very large proportion of my own 

 woik, which is a continuation of that begun by Weismann, and 

 was, in fact, inspired by it. 



Edward B. Poulton. 



Oxford, December 15. 



NO. I 1 56, VOL. 45] 



My friend Prof. Meldola has drawn my attention to a com- 

 munication by Mr. F. E. Beddard in Nature of November 26 

 (p. 78), in which the view is expressed that the brimstone butter- 

 fly (Gonepteryx rhamni) is rendered protected or unpalatable by 

 the yellow pigment of its wings being due to a substance formed 

 as "a urinary pigment," and that the coloration is "a conse- 

 quence of the deposition in the integument of bitter pigments." 



The following objections may be urged against the view that 

 this coloration, said to be of the nature of a " urinary pigment," 

 I affords any protection whatever. 



{ Gonepteryx rhamni itself has its female much paler than the 

 I male and of a greenish-white hue, whilst the wings in both sexes 

 are of a leaf-like appearance, which can only be due to the pro- 

 cess of natural selection, and can scarcely have been exercised 

 in the direction of "protective resemblance " if the insect was 

 already unpalatable by the "urinative" nature of the yellow 

 pigment of its wings. 



Yellow Lepidoptera have certainly no immunity from the 

 attacks of birds ; on the contrary, the scanty records we possess 

 of these onslaughts go to prove that the contrary is the case. 

 The late Mr. P. H. Gosse observed one of the greenlets ( Viero- 

 sylvia calidris) to pursue a species of Terias in Jamaica ("Birds 

 of Jamaica," p. 194), In Southern India, Mr. E. L. Arnold 

 found the principal victims of the green bee-eaters to be speci- 

 mens of Terias hecate['' On the Indian Hills," vol. i. p. 247-48). 

 Quite recently in the Transvaal I have observed the wagtail, 

 Motacilla capensis, to pursue and devour the yellow Lithosiid 

 moth, Binna Madagascar iensis. 



But the facts of " mimicry " seem to effectually dispose of the 

 supposition. In South Africa, the yellow black-margined 

 Papilio cenea affords by its females the most striking examples 

 to prove the non-protective value of this coloration ; for the 

 females respectively mimic those two well-known "protected 

 butterflies," the blackish Amauris echena and the reddish 

 Danais chrysippus, whilst, to add to the negative evidence, the 

 yellow male has been seen by Mr. Weale to become the prey of 

 the flycatcher, Tchitrea cristata. 



On the Amazons, Mr. Bates has long since shown that the 

 yellow and black Leptalis arise mimics the markings — even to 

 the colour of the antennae and the spotting of the abdomen — of 

 the protected or unpalatable Methona psidii. 



Russell Hill, Purley, Surrey. W. L. Distant. 



A Difificulty in Weismannism. 



In his communication of November 28 (Nature, December 

 3, p. 102), Prof. Hartog asks us to believe that Weismann, in 

 a letter from which he quotes, insists (i) that the Ahnenplasmas 

 are "not completely unchangeable," and (2) that "each 

 Ahnenplasma unit corresponds to an individual of the species 

 itself ; and if put under suitable trophic conditions would, singly, 

 reproduce such an individual." 



Assuming that thesis II. adequately represents the Freiburg 

 Professor's latest views, and that a few sentences detached from 

 their context are to be depended upon, we must, it seems to me, 

 conclude, with Prof. Hartog, that he has unearthed an incon- 

 sistency, and, what is of more importance, shown that the 

 shuffling process is not only unnecessary, but that a new signi- 

 ficance must be found for it. 



I am, however, still inclined to believe that hypothesis B is 

 the one upon which Weismann has founded his theories of 

 heredity and sexual reproduction. The hypothesis, however, 

 should take account of the variability, slight though it may be, 

 of the Ahnenplasmas. We agree to call the Ahnenplasmas 

 Protozoan, simply because we have no conception of the kind 

 and amount of the variation they have undergone since they 

 parted company with the unicellular organisms in which they 

 originated. We have no reason, however, to believe that the 

 external causes which led to their variation in unicellular organ- 

 isms are powerless to affect them now that they are localized 

 in the reproductive cells of multicellular ones. 



Prof. Hartog, moreover, while relinquishing the idea of the 

 variability of the offspring of the lioness, endeavours from 

 another point of view to attack Weismannism on the plane of 

 hypothesis B. Is he, too, sceptical as to Weismann's adherence 

 to hypothesis A, or does he simply wish to overwhelm the 

 so-called disciples ? 



In either case, several objections may be made to his argu- 

 ment. In the ftrst place, we object most emphatically to any 



