Mav 27, 1922J 



NA TURE 



^72> 



chemist with the necessary scientific insight, who would 

 take the time and pains required to become master of 

 the method, would find in it a weapon of research of 

 no mean value. 



Some misprints, one or two of which may at first 

 sight rather puzzle the reader, occur. The collection 

 of the whole of the plates at the end of the volume is 

 a great convenience, as the same plate is frequently 

 referred to in different parts of the text. One sug- 

 gestion we should like to offer in this connection, and 

 that is that the author should provide some key to 

 these very beautiful reproductions of his photographs. 

 It is sometimes extremely difficult for one not versed 

 in the art of reading positive ray photographs to pick 

 out the particular lines referred to in the text from 

 the considerable number which often appear on the 

 corresponding plate. We hope that Sir J. J. Thomson 

 may be prevailed upon to make this concession to 

 human weakness when, at some date which cannot 

 be very far distant, he makes a further revision of the 

 book for its next edition. J. A. C. 



Metamorphoses of Insects. 



Insect Transformation. By Prof. G. H. Carpenter. 

 Pp. xi + 282 + 4 plates. (London : Methuen and Co., 

 Ltd., 192 1.) 125. 6d. net. 



METAMORPHOSIS in the animal kingdom may 

 be approached from two angles of vision. 

 We may regard it solely as a preparation for the adult 

 condition that follows upon it, or we may consider it 

 from the point of view of recapitulation of racial 

 ancestry. In reality it is the result of the working of 

 both those factors. Among insects, the higher one 

 ascends among the orders of that class, the more the 

 evidence of recapitulation becomes obscured by 

 secondary' changes. Divergence in evolution has 

 occurred between the preparatory and final stages of 

 life. The more highly specialised the perfect insects 

 become the more their larvae degenerate. It is the 

 inert, legless, eyeless, and often headless maggot that 

 gives rise to the highest expression of insect life. The 

 active " intelligent " type of larva, endowed with limbs 

 and well-developed organs of special sense, is destined 

 to produce an imago lower in the scale of evolution 

 than that which arises from the degenerate larva 

 previously mentioned. 



In the springtails there is no metamorphosis. In 

 the locust and the plant-bug metamorphosis is clearly 

 evident, although the young are not very different 

 from their parents. Such insects pass through no 

 pupal stage, and their wings are formed externally. 

 NO. 2743, VOL. 109] 



In the majority of insects, however, whether they be 

 beetles, butterflies, bees, or flies, the young or larvae 

 are vastly different from their parents and a pupal 

 stage has become intercalated in the ontogeny. In 

 insects of this kind the wings arise as impushed imaginal 

 buds and reveal themselves outwardly only when the 

 pupal stage is assumed. 



In Prof. Carpenter's book we have a lucid account 

 of the various aspects of the above phenomena. It is 

 elementary, but not unduly so, and there are few 

 biologists who will not benefit by assimilating its 

 contents. The author devotes about two dozen pages 

 to describing the essential features of the morphology 

 of an adult insect. These pages contain nothing that 

 is .new to the entomologist, but they enable the more 

 general reader to obtain a better understanding of the 

 book as a Vhole. The following chapter is devoted to 

 the discussion of the metamorphoses of insects with the 

 open type of wing-growth. This is succeeded by a 

 detailed treatment of the higher orders of insects the 

 wings of which develop from concealed imaginal buds. 

 The remaining chapters treat of wingless insects, the 

 significance of metamorphosis in classification, the 

 surroundings of developing insects, and the various 

 problems of metamorphosis. 



The author has marshalled his facts into a continuous 

 whole with conspicuous success. He leads the reader, 

 step by step, through the increasing complexities of 

 metamorphosis in what we believe to be their true 

 evolutionary sequence. He attempts no new theories 

 nor does he throw fresh light on existing theories. He 

 prefers to draw extensively upon the results of recent 

 research and show them in their true perspective. The 

 book consequently represents very completely the 

 present-day point of view. The discussion of larval 

 and nymphal stages naturally occupies a large part of 

 a work of this nature. Prof. Carpenter evidently does 

 not concur with Comstock in his use of the term nymph, 

 and rather adopts the definition that applies it to all 

 exopterygote insects when the latter are in a stage in 

 which the wing rudiments can be distinguished clearly 

 by the naked eye. The expression nymph, however, 

 is a conventional one, and in reality all nymphs are, in 

 the zoological sense, larvae. 



The book is one which imparts a true appreciation 

 of how the details of the life-histories of different types 

 throw light on the development of insects as a class. 

 It is well printed and adequately illustrated with 

 figures largely borrowed from the writings of con- 

 temporaries, or from Prof. Carpenter's own publications. 

 Few scientific works have been issued since the war 

 at so reasonable a price, which is a matter for con- 

 gratulation to the author and publishers alike. 



A. D. Imms. 

 Z I 



