CHAPTER III. 



ON THE IMPORTANCE OF THE COLLExMBOLA AND THYSANUEA 

 IN RELATION TO THE EVOLUTION OP THE INSECTA. 



The Thysanura and Collembola possess a peculiar 

 interest from the position wliicli they appear to occupy 

 in the evolution of insects. 



It has always seemed to me that the metamorphoses 

 of insects are among the principal difficulties of the 

 Darwinian theory. Take, for instance, the life-history 

 of a butterfly. It commences as a caterpillar, with 

 powerful jaws adapted for cutting and masticating 

 leaves, then passes through a period of fasting, and in 

 its pel feet condition has a very complex suctorial 

 mouth. I omit for the present the consideration of 

 the development of wings and the changes in the in- 

 ternal org-ans. Now, how can such a case have arisen ? 

 It is obviously not an instance of contmuous evolu- 

 tion, because a mature Arthropod can never have re- 

 sembled the mouthless, motionless, imbecile Pupa. 

 I have often wondered that the opponents of Mr. 

 Darwin's views have not dwelt on these facts, which 

 pi^imd facie appear to present a strong argument 

 against the theory of evolution. 



On this interesting problem the Collembola and the 

 Thysanura seem to me to throw much light. I have 

 already discussed it briefly in my memoir on the 

 development of Ghloeon,^ and it has also been handled 

 by F. Miiller, Haeckel, Brauer, and by Mr. Darmn 

 himself. 



1 ' Liiin. Trans.,' 1863 and 1865. 



