396 E. R. Downie, 
Spermatogonia of second generation Synapsis. 
As the daughter cells are separated new nuclear membranes 
form and the daughter cells are the spermatogonia of the second 
generation. At first the nucleus of the spermatogonium of the second 
generation stained with iron haematoxylin appears uniformly deep 
blue black. It would seem as if the chromatin were diffused throughout 
the nucleus. Later the deeply stained area may be crescentic or 
localized in several rings. With the transparent safranin stain at 
this stage, however, while the deep stain of the nucleus shows much 
diffused chromatin the chromomeres can yet be distinguished per- 
sisting as twenty-four distinct bodies. This is the resting stage or 
synapsis. In the early part of this stage the centrosomes disappear, 
at least no stain has been tried which will make them apparent. 
Spermatocyte of the first order. 
This cell (Fig. 42) must now be considered the spermatocyte of 
the first order, since from it are derived the four spermatids and 
since the reduction in the number of chromosomes occurs in it. 
However the growth period which in higher animals marks the 
transition of the last generation of spermatogonia to spermatocytes 
seems wanting in Hydra. There is however a period of protracted 
rest in which the nucleus remains granular from the prominence of 
the chromomeres (Fig. 41). By using the extreme rather than the 
average cell measurements, there could be introduced another genera- 
tion of spermatogonia followed by the typical growth period. But 
the evidence seems to be against such a third generation of sperma- 
togonia and it is the exceptional measurements rather than the 
average which support such a possibility. The measurements will 
be given later. 
It is interesting to note a difference in the method of karyo- 
kinesis in those spermatogonia which are found occasionally dividing 
at the very margin of the spermary, for they mark a transition to 
the type of division by which the interstitial cells usually divide. 
The preparation for division up to the appearance of the spireme 
stage is as already described. Then gradually the mesh work of 
strands is replaced as one connecting thread after another disappears 
until only a single continuous thread remains with the chromomeres 
beadlike on it. This thread takes the stain more and more intensely as 
the chromomeres disappear. Finally the thread is smooth, showing 
