384 E. R. DowxixG, 
Specimens of H. fusca were observed from the time the first indica- 
tions of testes could be detected as minute swellings. In early 
September a testis is formed, matured, discharges its sperm and 
disappears in about twenty-four hours. Within a short time after 
the first appears, others follow, perhaps are synchronous in appear- 
ance with the first. The testes usually begin to appear about the 
time the ovaries are matured. The sequence of events is the same 
for H. viridis, though so far as my observations go it seems less 
proterogynous, the testes appearing about the time the egg is dis- 
charged. This statement contradicts the one made by W.MarsHALL (64) 
who says in regard to H. viridis that by the end of May the 
testicles discharge their sperm, although the eggs do not show them- 
selves before the end of September. It seems probable that altering 
conditions change the breeding habits of Hydra. At least it is 
difficult to harmonize the statements made by different observers as 
to times and conditions of breeding on any other basis. I think 
this statement of MarsHALL'S might readily be accounted for by as- 
suming that he saw the end of one reproduction cycle — the testes being 
present — and the beginning of the next when the ovaries appeared. 
These three species produce few ovaries and testes — one or two 
of the former and four or five of the latter being the rule. If an 
individual produces an unusually large number ot ovaries, testes and 
ovaries will both be present, and it must be remembered that it is 
a frequent occurrence to have testes and ovary appear synchron- 
ously. 
Testes in H. dioecia. 
In H. dioecia the testes may be very numerous and appear 
on the entire body except the very foot and immediately under the 
tentacles. Fig. 10 shows such an animal copied from Braver. It 
is more completely covered than any animal observed by the present 
writer, although twenty-eight testes on a single Hydra have been 
counted. In this species the ovaries may be numerous too, and each 
may give rise to several eggs (Fig. 6 and 7). We have then in 
these closely related species conditions varying from synchronous 
appearance of the testes and ovaries through proterogyny to dis- 
tinct sexes. 
Form of testes. 
The testes appear in surface views as minute elevations, conical 
at first but as growth occurs they become mammiform. Toward 
maturity the tip is seen to be full of sperm freely and rapidly 
