THE SPERMATOPHORE IN ARENICOLA 1013 
delay division until well out toward the periphery. The inter- 
mediate sizes may be scattered, with no apparent order, through- 
out the organ. Not infrequently, cells of the third or even sec- 
ond generation reach the edge and are broken from the mass tc 
float in the body fluid separately or in larger or smaller groups. 
But frequently the typical arrangement described will hold for 
large regions of the gonad. ‘The peripheral cells tend to cohere 
into roughly spherical masses of from ten to fifty or so cells all in 
the same stage of division and these break away into the body 
-eavity. But smaller masses of cells may be detached, even single 
cells. In the body fluid division continues rapidly as will be 
described shortly. 
THE SPERMATOPHORE 
Formation 
The largest spermatogonia, immediate descendants of the peri- 
toneal cells, may be called the primary spermatogonia. During 
the year, except just before the height of the breeding season, 
these primary spermatogonia multiply, and after division, the 
daughter cells grow to the size of the parent cells except toward 
the periphery of the gonad. In the late fall and winter, in A. 
cristata collected at Woods Hole, the gonad is largely made of 
_ the primary spermatogonia; it presents quite a solid appearance. 
In the spring, however, division of these cells ensues so rapidly 
throughout the gonad, as it always does at the periphery, that 
the secondary spermatogonia do not have time to become as 
large as the primary ones before they divide in turn. Now the 
division of the cells derivative from a single primary spermato- 
gonium, after it starts on its course of rapid subdivision, seems 
always to be roughly synchronous. The gonad taken during the 
fall and winter presents a somewhat mottled appearance along 
the margin when sectioned and stained, due to the prominence 
of these masses of cells in division among the relatively inactive 
primary spermatogonia. In the spring this mottled appearance 
pervades the whole gonad, for here and there a primary spermato- 
gonium will start on its course of rapid subdivision, giving rise 
to two, then four, eight, etc., cells, which at first lie close together 
