1014 ELLIOT ROWLAND DOWNING 
as a solid mass, but later have a cavity at the center, the segmen- 
tation cavity. These forming spermatophores, for such they are, 
move to the periphery in order to break away into the coelomic 
fluid. So in spring and early summer the gonads have, when 
sectioned, a very ragged appearance. Deep bays and systems of 
lacunae run into the mass so that the spermatophores may be 
discharging not only at the periphery but are moving out from 
many spots in its interior (figs. 7 and 8). 
There is frequently protoplasmic material at the center of this 
early spermatophore. It is derived from the disintegration of - 
cells which, while the spermatophore is forming in the body of 
the gonad, come to assume a central position. Degeneration 
goes on as the cells move toward the margin of the gonad so that 
by the time the margin is reached little is left of the central cells. 
Occasionally strands of protoplasm run from some of the cells 
to a central point (fig. 15), suggesting a figure such as Calkins 
has shown for Lumbricus, as if the cell walls formed peripherally 
before they do centrally. This is an exceptional condition, how- 
ever, and I am confident that no such interpretation is to be put 
upon it in Arenicola. Figure 16 is much more usual. In the 
more mature spermatophores one can, by carefully tapping the 
cover glass, cause the spermatogonia to break away from the cen- 
tral portion, leaving it as a colorless sphere containing occasion- 
ally a few granules. This does not ordinarily stain, has slight 
consistency and seems like a drop of slightly viscid fluid. Not 
infrequently even this disappears and the spermatogonia break 
away without leaving any residual mass. The central cells are 
then absorbed very early and the central remnant is possibly 
excretory in its nature, the products of anabolism that have diffused 
into the cavity. 
Discharge of the forming spermatophore 
The cells are customarily discharged, as has been stated, from 
the surface of the testis into the body cavity in roughly spherical 
masses. The constituents measure about 6u in diameter in A. 
cristata. Three divisions at least follow and probably more, 
