ACCOUNT OF THE GERM-CELL CYCLE 31 
example, in Miastor the single primordial germ cell 
produces eight; in the beetle Calligrapha multi- 
punctata the original sixteen undergo two divisions 
resulting in sixty-four; and in the chick Swift (1914) 
has counted as many as eighty-two at this stage. 
We shall see later that the primordial germ cells 
are often characterized by the presence of certain 
cytoplasmic inclusions (the keimbahn-determinants) 
which are absent from the other cells of the embryo. 
These inclusions appear to be equally divided be- 
tween the daughter cells so that each of the eight or 
sixty-four, as the case may be, is provided with an 
equal amount of the keimbahn-determinants. 
3. Pertop oF “Rest” anp Micration. By rest 
here is really meant cessation of division. During 
this period the germ cells either actively migrate 
or are passively carried by surrounding tissues to 
the position the germ glands occupy in the larva. 
In species possessing two germ glands the germ cells 
separate to form two groups, with, at least in some 
cases, an equal number in each group. Thus in 
Miastor the number in each group is four (Fig. 22) 
and in Calligrapha, thirty-two (Fig. 37). There is 
evidence that an active migration of germ cells 
occurs both in vertebrates and invertebrates. Figure 
6 shows the positions of the germ cells in four species 
of vertebrates during their change of position. 
That the germ cells at this time are actively migrat- 
ing by ameboid movements is the general opinion 
of investigators, since frequently these cells are 
ameboid in shape and the distance between the place 
