NA TURE 



[November 4, 1897 



stated, of Calocampa exoleta, &c., to sticks, is intended. 

 One is at a loss to understand why some ancestral time 

 at which Haase imagined that food was especially scarce, 

 and the enemies of insects especially keen, should be 

 spoken of as a " Palaeolithic Period" (p. ii8). 



At the end of the volume the author contributes a 

 section, entitled " Mimicry a form of protective adapt- 

 ation to the environment" (pp. 145-151). In these pages 

 he treats, in a very inadequate manner, of protective 

 resemblances in general. The important and wide- 

 spread cases of variable colour resemblances he does 

 not even mention. The attempt is made to distinguish 

 between protective resemblance and mimicry on the 

 ground that the latter is an imitation of moving objects, 

 the former of motionless ones. This distinction, which 

 has been drawn before, seems to the present writer to 

 be unreal, and, so far as it holds, to be of little import- 

 ance as a basis for classification. There are many ex- 

 amples of the protective resemblance of moving objects 

 — butterflies and moths which resemble leaves whirled 

 along by the wind ; larvae and cocoons which resemble 

 sticks, &c., swinging by a thread. The essential dis- 

 tinction lies in the fact that in protective resemblance 

 the model is of no interest to the enemies of the imi- 

 tator, while in protective mimicry the model is dreaded 

 or disliked by the enemies ; the effect of protective 

 resemblance is concealment ; the effect of protective 

 mimicry, conspicuousness. 



In this section the wonderful resemblance of butter- 

 flies of the genus Kalliina to dead leaves is briefly dis- 

 cussed, and the author concludes (p. 147) that 



" the extraordinarily manifold variations among Kallima, 

 &c., show, not only that these so perfect resemblances 

 of withered leaves, and often of those covered with rust- 

 fungus or partially eaten by larvie of Agrotnysa., are the 

 highest development of mimicry of leaves, but they also 

 indicate that these are the youngest forms, and are still 

 under the influence of natural selection, which will 

 gradually obliterate that which is less fitting." 



It is, of course, very improbable that a species which 

 has attained the highest development in any character 

 could still remain in the formative stage as regards the 

 very same character. As a matter of fact, the " extra- 

 ordinarily manifold variations" of Kalliina are not the 

 ordinary individual differences upon which natural selec- 

 tion acts, but rather certain varied forms into which 

 the species has been thrown by natural selection, causing 

 it to resemble not one, but many of the appearances 

 presented by dead leaves, and thus conducing towards 

 its protection. This high product of selective action has 

 been mistaken by Haase for the mere material for 

 selection to begin its work upon. 



There are some excellent pieces of work and interesting 

 suggestive inferences to be found in the memoir — not to 

 be compared to the great hypotheses connected with the 

 names of Bates, Wallace, and Fritz Miiller, but valuable 

 additions to the subordinate parts and details of the 

 subject. 



Of this kind is the discussion on mimicry in the 

 PapilionincE (pp. 80-95), to which Haase has given 

 special attention, and which forms the subject of Part i. 

 of his work, as yet untranslated into English. In this sec- 

 tion he produces evidence that the species of Papilio 

 NO. 1462, VOL. 57] 



which are especially mimicked by others belong to the 

 genus Pharmacopkagus, and, as he thinks, derive their 

 qualities from the poisonous or acrid larval food. 



The contention (p. 97) that specially protected butter- 

 flies but rarely avail themselves of a distinct and markedly 

 conspicuous " warning colour," that " among the Neo- 

 tropincE in general the wing-colouring, with its brilliant 

 yellow, rusty-brown and black, is more beautiful than un- 

 pleasant," must be admitted to be true ; the conclusion 

 was, in fact, stated in 1890 by the present writer, who 

 also pointed out that a conspicuous appearance is never- 

 theless attained because " the colours spread on the parts 

 which are exposed during rest, and the flight becomes 

 sluggish, so that they are displayed as completely as 

 possible" ("Colours of Animals," Lond., 1890, p. 191). 



On p. 106 we meet with an interesting case (that of 

 four white spots on the outer margin of the hind wing of 

 the female vSiY. proiogcnia of Elyinnias undularts, Dru.), 

 in which it is argued with force that changes caused by 

 reversion to an older type of marking have been made 

 use of to aid a mimetic resemblance. In a note on the 

 same page, Haase brings forward Cethosia cyane, Dru., as 

 a unique example of a closer resemblance on the part of 

 the male than the female to another specially defended 

 insect — Danais chrysippus. He makes the very probable 

 suggestion that the Cethosia is also itself specially 

 defended. 



Interspersed with much almost worthless speculation 

 there is a great deal that is suggestive and valuable 

 in the analysis of the various patterns of those Neo- 

 tropince which are resembled by other butterflies, includ- 

 ing many belonging to different sections of the group 

 itself (pp. 116, 117). The various tables embody an im- 

 mense amount of careful comparison and the examination 

 of a vast number of specimens ; they will prove of the 

 highest value to future workers. E. B. P. 



{To be continued.) 



A DEVONSHIRE GEOLOGIST. 

 A Memoir of William Pengelly, of Torquay, F.R.S., 

 Geologist, with a Selection from his Correspondence. 

 Edited by his daughter, Hester Pengelly. With a 

 summary of his scientific work, by the Rev. Prof. 

 Bonney, F.R.S. 8vo. Pp. xi 4-341 ; with portrait and 

 10 illustrations. (London : John Murray, 1897.) 



THE story of William Pengelly is one of the pursuit 

 of knowledge under difificulties, and of the achieve- 

 ment by the hero of an honoured place amongst those 

 who have rendered distinguished service to science. 

 Many of his paternal ancestors were sailors, and his 

 father was captain of a small coasting vessel, in which 

 his son William accompanied him, after receiving an 

 elementary education at East Looe in Cornwall. For 

 four years the lad was engaged in a seafaring life, but 

 in 1828, at the age of sixteen, and at the earnest desire 

 of his mother, he returned to his native village, and was 

 occupied for a few years in active manual labour. He 

 had, however, developed a passion for learning, and 

 every hour that could be spared, was devoted to the 

 acquisition of knowledge, and more especially of mathe- 

 matics. Having so far prepared himself, after severe 



