INTRODUCTION 



mens of Apus cancriformis, and Professor Biedermann, 

 of Jena, very kindly obtained for me specimens of 

 Apus cancriformis, Lepidurus productus, and Branchi- 

 pus stagnalis from Prague, especially preserved for 

 histological purposes. An examination of the Spitz- 

 bergen specimen led to the conclusion that it 

 was a small variety of Lepidurus glacialis, which 

 I propose to call Lepidurus Spitzbergensis ; the 

 grounds for this determination are given fully in 

 Appendix I. 



In studying the anatomy of the Spitzbergen 

 specimens, and in comparing it with that of the other 

 members of the family kindly placed at m)- disposal 

 by the gentlemen above named, I was gradually led 

 to cast my notes into the form in which they are now 

 published. 



It has long been recognised that the Ph)'llopoda 

 possess many markedly Annelidan characteristics, and 

 that they are therefore, of all living Crustacea, nearest 

 in affinity to the primitive Crustacean. In m}- study 

 of the Apodidae I was so much struck by the resem- 

 blance between the organisation of Apus and that of 

 a carnivorous Annelid, that I finally decided to work 

 entirely along this line. I resolved, by a closer study 



