HYDRA: ITS ANATOMY AND DEVELOPMENT. 327 
From this time a greater change took place; the portion which 
formerly was the free end of the tentacle became very much 
swollen and rounded. I also discerned three distinct parts forming. 
(Fig. 81.) And after careful watching, I found that the free end of 
the tentacle became larger and larger, and that the lower portion 
became narrower, and eventually formed foot; the free end of the 
tentacle at the same time forming the future head. 
This was observed in twenty-four hours after severance, as re- 
presented in Fig. 81. Thus, you see, what was formerly the upper 
part in Fig, 80 is now the lower part in Fig. 81. 
In forty-eight hours, as represented in Fig. 82, the tentacle was 
shaped like a minute Hydra, without tentacles ; the body was well- 
defined and properly upright, having fastened itself by the lower 
part (which I now call the foot) firmly to the glass. 
On the upper surface two minute processes could be seen; and 
for some time after this it continued to develop in bulk, except 
the processes last mentioned. 
In seventy-two hours, by Fig. 83 it will be seen that it had in- 
creased in size nearly double what it was as represented in the 
preceding figure. For three days no change could be observed ; 
but on the seventh day three distinct processes could be plainly 
seen, which developed into tentacles. (Fig. 84.) On the tenth 
day five tentacles were seen without the aid of a glass. (See Fig. 
85.) The body had lengthened itself, and the foot-stalk was easily 
made out with the aid of a lens. 
It continued to develop, and on the fifteenth day (Fig. 86) it 
had seven tentacles, and the body, when in the contracted state, was 
very much larger than the polype of which it had previously formed 
a part. Up to this time it had not partaken of any food, but now 
its arms began to play freely, and, for the first time, it caught 
Daphnia pulex, and in two hours I noticed that it partook of food. 
The polype, now a perfect Hydra, having taken fifteen days from 
the time of division to that of perfection. 
This experiment I have repeated on several occasions this year. 
We will now turn our attention to the Hydra of which the ten- 
tacle had formed a part (Fig. 87), and which had been divided 
through the mouth and body. 
For three hours it lay curled up at the bottom of the glass. 
During the following hour the cut parts extended themselves, and 
the foot attached itself to a leaf. The parts at the outer edge 
were very dark in colour, some of which sloughed away. In 
five hours after division these dark spots could no longer be 
seen. ‘The tentacles began to move freely in the water, and at the 
posterior end of the cut portions, the outer edges were slightly 
rounded, and evidently being drawn together. 
In twenty-four hours it was still in the same state. 
