162 GERM-CELL CYCLE IN ANIMALS 
definite number is not required, and the germ cells 
become generally distributed throughout the cellular 
mass before budding begins, the chances are that 
every bud will contain one or more germ cells. For 
example, if germ cells occur in all parts of the blas- 
toderm of the armadillo, as is quite possible, each of 
the four embryos must become provided with a por- 
tion of them. On the other hand, the germ-plasm 
may be rather widely distributed among the cells 
and only becomes segregated in germ cells after bud- 
ding takes place. Careful studies of the germ-cell 
history in polyembryonic species are much needed 
and would no doubt produce important results. 
The data presented in this chapter are sufficient 
to prove that in many insects a complete germ-cell 
cycle can be demonstrated. There are many species, 
however, in which no early segregation of germ cells 
has been discovered even after very careful examina- 
tion. It is therefore too early to make any general 
statements for the entire class, but we must base our 
conclusions regarding the germ-cell cycle upon our 
knowledge of those forms in which the keimbahn 
actually can be traced. Finally one point should be 
emphasized; in every case the segregation of the 
primordial germ cells is intimately associated with a 
substance which can be made visible by proper 
staining methods. In Miastor this is the pole- 
plasm; in Chironomus the “Keimwulst” or ‘‘Keim- 
bahnplasma”’ ; in Calliphora the “‘Dotterplatte” ; 
in chrysomelid beetles the pole-disc; and in parasitic 
Hymenoptera, the keimbahn-chromatin. The na- 
