The spermatogenesis of Hydra. 383 
until Braver clearly recognized the difference. If any of the numer- 
ous attempts to establish new species of Hydra have been based 
on observations of this species the descriptions are not sufficiently 
accurate to permit of its recognition. 
It seems almost invidious to introduce another name into the 
already confused mass of specific names heretofore applied to Hydra, 
and yet it seems impossible after going over the literature to adopt 
any of the specific names already used without again confusing this 
clearly marked species with the others previously recognized, espe- 
cially H. fusca. The most striking character of the species is that 
the sexes are distinct. BRAUER, who noticed this first, had the 
animals under observation for many months. It is not uncommon 
to find individuals of the other species with only testes or ovaries 
present, i. e. proterogynous, but the majority have both at the same 
time. In the hundred and more individuals of ‘A. spec.” observed 
sexually mature in the present investigation, none have been seen 
with both ovary and spermary, so that these observations, though 
not as extensive as BRAUERS, confirm his in this character. The 
figures of male and female are given in Fig. 6 and 7. I would 
prepose for this ‘H. spec?’ of Brauer the specific name dzoecia. 
The three species grisea, fusca and dioecia, according to 
Harcirr as quoted, would have to be considered the same. But 
the characters just given are sufficiently exact to warrant terming 
them distinct species. Possibly they may be found to be the same 
animal assuming different form, structure, relative size of parts and 
habits under varying conditions. But it would seem less probable 
than that H. viridis was merely a H. fusca containing symbiotic 
algae. Until they are demonstrated to be varieties, it will be wise 
to recognize the four species. , 
Zone of the testes. 
The testes develop in the three hermaphrodite species in a zone 
extending from just below the tentacles to a point perhaps a half, 
though usually not over a third of the way to the aboral end. Those 
testes nearest the tentacles are the least mature. The ovaries are 
produced on that third of the body just below the zone of the testes. 
Proterogony. 
In these hermaphroditic species, the animals are usually pro- 
terogynous, the ovaries maturing before the testes are formed. 
