1020 ELLIOT ROWLAND DOWNING 
After my attention had been caught by the peculiar egg-like 
cleavage of these giant spermatogonia which float freely in the 
body fluid, I hunted carefully for the early developmental stages 
of the normal sized spermatogonia that are occasionally set free 
singly in the coelom. So far as I can find, their development is 
the same as that just described for the giant form. 
One other interpretation might be suggested for these giant 
cells, namely, that they are tiny eggs which cleave in the body 
fluid to a certain point and then disintegrate. It is well known, 
of course, that such hermaphroditism of the gonad occurs when 
degenerative changes are going on init. But such an explanation 
seems negatived in this case by the following considerations— 
1. If they are developing eggs they would be undergoing cleay- 
age long before they reach normal size, in fact when only about 
one four-hundredth of the size of the egg when it is normally 
ready to be fertilized and begin cleavage. 
2. The normal sized spermatogonia undergo a similar cleavage 
when they are liberated singly in the body fluid. 
3. At the height of the breeding season, when these so-called 
giant spermatogonia are present, there are also found quite fre- 
quently giant spermatozoa whose volume bears about the same 
relation to the volume of the normal sized sperm as the volume 
of the giant spermatogonia bears to the volume of the usual pri- 
mary spermatogonia. ; 
It is to be noted that these exceptionally large spermatogonia 
appear toward the close of the breeding season. It is at this time 
that the body fluid is supercharged with spermatophores, evi- 
dently taxing the respiratory and excretory organs to the limit 
of their capacity. For it is at this time that the blood vessels 
develop in numbers like a thick growth of hair on the first and 
second nephridia and the adjacent muscles in A. cristata and in 
similar positions in the other species. At this time, too, the gonad 
is invaded by phagocytes, while the portions adjacent to the blood 
vessel suffer fibrous degeneration. It seems quite likely then, 
since the respiratory organs are taxed to the utmost, that an oxy- 
gen starvation sets in in the gonadial tissue, inducing fibrous 
