CHAPTER V 



THE SEGREGATION OF THE GERM CELLS IN 

 THE ARTHROPODA 



1. The Keimbahn in the Insects 



The insects have furnished a very large proportion 

 of the data upon which many of our biological 

 conceptions are now based, and they are becoming 

 more and more popular for studies of the physical 

 basis of heredity, and for purposes of animal breeding. 

 It was in insects (Miastor) that the early segrega- 

 tion of the germ cells in animals was first definitely 

 established. The accessory chromosome was dis- 

 covered in insects by Henking in 1891, and our 

 knowledge of the chromosomes, which has increased 

 so remarkably within the past fifteen years, is due 

 principally to the study of oogenesis and spermato- 

 genesis in insects. In this chapter the chromosomes 

 will only be considered incidentally, a more detailed 

 account being deferred until later (Chapter IX). 

 The early history of the germ cells in insect develop- 

 ment has not been slighted, for there are many 

 reports based on this subject alone and still more 

 data hidden away in contributions on general em- 

 bryology. It will be necessary here to select from 

 this abundance of material those reports that give 

 us the clearest pictures of the keimbahnen. As 



106 



