November io, 1892] 



NA TORE 



29 



throughout to give me the sole, or, at any rate, the chief, re- 

 sponsibility for both hypothesis and examples. 



In writing my book I made great use of a very interesting 

 series of specimens in the Museum of the Royal College of Sur- 

 geons, lately brought together by Prof. Stewart. The aggressive 

 mimicry of the VolucelUs was illustrated in one of these cases, 

 and I briefly described the contents of the case in the passage 

 Mr. Bateson quotes. I was glad to give a few more details 

 than those supplied by Mr. Wallace, and at the same time to 

 mention examples which could be actually seen by readers ; 

 for I referred to the collection more than once. I was, however, 

 anxious to obtain confirmation from one who had studied the 

 Hymenoptera and their parasites much more minutely than I 

 had, so I referred the proofs to Mr. R. C. L. Perkins, a most ob- 

 servant naturalist, specially interested in these insects. He made 

 some valuable suggestions, but did not modify the account of 

 the case in the Royal College of Surgeons. I think I may 

 claim, therefore, that I took all reasonable precautions to avoid 

 error in a part of the subject which had not then come under my 

 own personal observation. Prof. Lloyd Morgan, in his interest- 

 ing " Animal Life and Intelligence," has also mentioned this 

 example, and figures the Volucella and Bomlms mtiscorum. He 

 tells me that his figures were copied from a case in the Natural 

 History Museum, so that my selection appears to be supported 

 by the two great biological museums of London. 



Within a few weeks of the appearance of my book, I had 

 found out the omission of the other banded humble-bees also 

 mimicked by the mystacea variety of Volucella bomhylans, and 

 I showed one of these (I think B. hortorum) at a lecture given 

 to the British Association at Leeds in 1890. I had intended, 

 and intend, to repair the omission in any reprint that may be 

 required . 



There is, however, nothing inaccurate in the statement that 

 B. musconim is mimicked. We require something more than 

 dogmatic assertions and question-begging metaphor of tabby-cat 

 and fox to establish this as an error of the two museums and the 

 two volumes which have followed them in this respect. Mr. 

 Bateson appears to have been studying the literature of Volti- 

 cellcE rather carefully ; if he now extends his investigations to 

 the perfect insects themselves, and compares the individuals in 

 a series of moderate length, he will find that the mystacea variety 

 differs much in the demarcation of its rings or zones, and also 

 that the appearance of each individual varies with the direction 

 from which it is observed. The less sharply-marked appear- 

 ances resemble B. muscorum, the likeness being increased by 

 a slight indication of zoning to be seen in the latter. 



On July 7 of the present year I captured, in a wood near 

 Newbury, a pair of the variety mystacea in copula. The 

 male, the larger insect, was unusually indistinctly zoned. I 

 have submitted the specimens to Mr Verrall, who kindly 

 tells me that the large male is certainly the variety fnystacea, 

 and he evidently thinks there is nothing remarkable about it. 

 On the other hand, the female, which was unusually small, is 

 more interesting, being somewhat an intermediate variety. As, 

 Mr. Verrall informs me, Rondani has made about a score of 

 intermediate species, this little capture of mine may turn out to 

 be of interest, and it is comforting in a controversy of this kind 

 to be able to add one fresh observation which may be of some 

 use, if only in the way of confirmation. 



Now as to the statement, in which no ambiguity was intended, 

 that the two varieties lay in the nests of the bees they respec- 

 tively mimic. This was, as Mr. Bateson says, a very gentral 

 impression, the impression of naturalists who knew these insects 

 far better than I did, an impression which had already been 

 expressed in the case at the College of Surgeons. If I was mis- 

 taken in adopting it, was it not well that I made the mistake, 

 if by its means the general impression should be corrected, 

 having in my book assumed a tangible shape? What man who 

 cares for the advance of science more than for his own advance- 

 ment would regret to have made a mistake under such circum- 

 stances ? 



But I am not yet satisfied that the impression is not substan- 

 ially correct. I do not regard the dimorphism of V. bomhylans 

 a< the unique phenomenon it appears to be in the opinion of 

 \\r. Bateson, I fail to see any essential biological difference 

 liitween it and the dimorphism of many Lepidopterous larvae — a 

 liiuorphism which extends into the pupal stage of most species 

 nf thegenus Ephyra — or between it and the distinct types into 

 which certain butterflies of the genus Kallima can be divided 



NO. 1202, VOL. 47] 



according to the colouring of the under sides of the wings, or 

 certain moths of the genus Triphcena according to that of the 

 upper sides ofthe upper wings. But we know that in those cases 

 which have been tested, while the majority of the offspring re- 

 semble the variety to which the parents belonged, a certain pro- 

 portion follow the other variety, and when the parents belong to 

 different varieties the offspring are more equally divided. It is 

 therefore only to be expected, so far as our present knowledge 

 goes, that both varieties should emerge from the same nest. The 

 important thing to be ascertained, from the point of view of the - 

 theory of aggressive mimicry, is not the colour of the off- 

 spring which emerge, although this is of high interest on other 

 accounts, but the colmr of the parents which enter. It might be 

 supposed that Mr. Bateson would have understood this, but it 

 is perhaps too much to expect from a critic who is so aggress- 

 ively uninterested. 



It would be interesting to know the grounds upon which Mr. 

 Bateson considers the dimorphism of V. bombylans to be almost 

 unique. At present he contents himself with assertions. If we 

 were ever to return to the regime of authority and dogmatism in 

 place of reason and experiment, Mr. Bateson's scientific position 

 would be indeed assured. 



Years ago I was satisfied that the evidence for the statement 

 in my book was insufficient, and this, too, I had intended to 

 modify when the opportunity occurred. In lecturing I have 

 often alluded to the investigation as an interesting one, and only 

 a fortnight ago suggested it to the members of the Natural His- 

 tory Society at Marlborough College. Two years ago I en- 

 deavoured to breed Volucella: in the manner described by Mr. 

 Bateson, I am sorry to say without success. I may therefore 

 claim that the statement quoted by Mr. Bateson had produced 

 no paralysis of effort on my part either as regards my own work 

 or that which I have been able to suggest to others. 



I may add that the upshot of this inquiry — even if it lead to 

 the conclusion that both varieties lay indiscriminately in the nests 

 of all the species they resemble — would not, in my opinion, 

 remove the Volucella from their place as examples of aggressive 

 mimicry, but the working of the principle would be more 

 complex. I do not, however, propose to render myself liable 

 to further sneers about "ingenuity" by discussing it on the 

 present occasion. 



Mr. Bateson's letter appropriately ends by putting into 

 my mouth a defence I should never have advanced — a 

 defence which was obviously inserted in order to impute 

 discredit — and then proceeding to the easy task of de- 

 molishing it. Let me therefore say that a mistake is to me 

 a mistake, whether in a volume intended for the public or a 

 paper presented to a scientific society. Indeed, I regret the 

 former more than the latter. Unfortunately, too, mistakes are 

 more liable to occur in the volume, because the ground is 

 wider, and passes in some directions into less familiar regions. 

 But I can honestly say that I have always done my best to 

 avoid mistakes, and that I correct them as the opportunity 

 arises, in fresh papers or in reprints of volumes. And I derive 

 much comfort from Mr. Phelps' dictum, which I am sure 

 appeals to everyone who works, that "people who never make 

 mistakes never make anything." Edward B. Poulton. 



Oxford, October 24. 



P.S. — I wish to take this opportunity of correcting certain 

 mistakes in my book (" Colours of Animals," Intemat. Sci. Ser.), 

 as it may be some time before the book can be reprinted, owing 

 to the number of copies struck off. 



Pages 49, 50. — Dr. Hurst informs me that my abstract of 

 Weismann's work on seasonal dimorphism is wrong. This will 

 be carefully reconsidered in any reprint. 



Page 73. — I wish to withdraw the account of Phrynocephalus. 

 Although the structures alluded to are probably alluring, there 

 is not sufficient evidence as to the manner in which they are 

 used. 



Page 85.— Professor Howes calls my attention to the descrip- 

 tion of the nerve-terminations in pigment-cells. 



Page 94, et seq. — Sir J. Ross should be Captain James Ross. 



Page 105. — I ought to have added that Mr. Sharpe's conclu- 

 sions are not accepted by Professor Newton. 



Pages 142-146. — Mr. Bateson has shown that the white 

 cocoons of Saturnia and Eriogaster are not due to the white 

 backgrounds employed, but to disturbance of the larvae. It 

 is still probable that the principle holds in Halias prasinatta:^ 



