THE SPERMATOPHORE IN ARENICOLA 1019 
especially true at the height of the breeding season. Spermato- 
phores containing such cells are produced, I take it, from the 
spermatogonia that are liberated singly from the gonad, notably 
the giant spermatogonia. The large cells are the macromeres 
and possibly some of the first quartette—in other words, the hom- 
ologues of the mesentomeres. The spermatophores consisting of 
a hundred or so cells never show such differences, all giving under 
pressure, the same so-called blastophore, apparently a drop of 
fluid, perhaps enclosed in a very delicate sheath, the fluid staining 
fairly deeply with methylen blue but scarcely at all with neutral 
red or other stains tried. It seems reasonably certain therefore 
that the invaginated mesentomeres disintegrate promptly to 
form the nutrition for the developing spermatophore. 
It is manifestly difficult to determine with exactness the order 
of cleavage and the relations of the cells. These enlarged sperma- 
togonia occur only at the height of the breeding season and then 
make up a very small per cent of the developing spermatophores - 
in the body fluid since these have been accumulated by the ordi- 
nary method for months. One must determine what occurs by 
the chance finding of successive stages, a laborious process, since 
the percentage of the desired material is so small. Presumably 
the cleavage of the giant spermatogonia might be watched if 
one could keep the body fluid under normal conditions. But it 
coagulates in the course of a few minyites after removal, the body- 
fluid cells cohere in masses and all other cells, too, cease their 
activity. When stages are found in the development of these 
giant spermatogonia it is not easy to determine the exact relations 
of the cells, for the cell mass is small and transparent, even if 
stained; furthermore it is difficult to manipulate the cell mass 
without breaking it as it is only about one four-hundredth the 
size of the developing egg. Still I am confident of the above 
statements, as I have worked with the living material, stained 
whole mounts and sections. The results stated have been re- 
peatedly confirmed during several summers at Woods Hole, 
working on A. cristata and have also been confirmed with the liv- 
ing and fixed material of A. claparedii and A. grubii. 
