CHAPTER V 
THE SEGREGATION OF THE GERM CELLS IN 
THE ARTHROPODA 
1. Tae KEIMBAHN IN THE INSECTS 
TuE 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 odgenesis 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 
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