28 . 
Klumenberg traced their origin in it from colourless bodies. 
Hamaan, on the contrary, states that they migrate into it from the 
endoderm ; but he appears to start from the point of view of their 
algae nature, and to be like some other observers ignorant of the 
fact that chlorophyll bodies multiply by fission. It may be added 
that Hydra viridis is unlike Spongilla or the Fresh-water Sponge ; 
(1) when confined in the dark it does not lose its colour, and that 
in some green varieties green angular bodies have been found 
similar to the colourless angular bodies of Hydra fusca which 
is brown in colour, the lower part of the body being attenuated into 
a kind of stalk, (2) the presence of small granular gland cells on 
the hypostume, (3) in having vacuolated gland cells at the base of 
‘the gastric cavity. 
According to Zickeli, cnidoblasts are present in the endoderm, 
while the chlorophyll corpuscles are present chiefly in the marginal 
part of the endoderm cells, and found plentiful in their base. These 
corpuscles are spherical and consist of an outer envelope containing 
the chlorophyll, usually entire but sometimes in plates, with 
central protoplasinic contents, and therefore resemble the chloro- 
phyll bodies of plants. 
With regard to its method of locomotion, Owen in his lectures 
on the Comparative Anatomy of Invertebrate Animals States. 
“* When the Hydra would change its position, it fixes one of its 
tentacles to some supporting surface approximate to the head ; and 
advances by leech-like movements. It can move in water as well 
as on a plane, for it would swim, suspended to the surface of the 
water by the foot, which is then exposed to the air; this disc then 
-dies, acts as a float and the Hydra can row itself along by one of 
its tentacles. Its ordinary position is one of rest.”’ 
Trembley formerly asserted that the animal could be inverted so 
that the ciliated epithelinum and hepatic cells were developed on 
what was the outer-surface of the thread—other ectodermal cells 
on what was the gastric surface, and by this means digestion would 
be effected as well on the outer as on the inner surface, and the 
animal continue to live. This view has however been disproved by 
“modern researches, 
The Hydra is mostly celebrated for its marvellous powers of 
reproduction. This is in the ordinary way achieved by germination 
or budding from any part of the body except the tentacles. 
Sometimes two or three are proceeding at one time from the same 
individual. A little tubercle rises en the body of the parent, which 
enlarges every hour, and ultimately tentacles appear at the apex, 
but no sooner are the young thus furnished than they commence 
catching prey on their own account whilst still attached to the 
body of their mother, but the bud ultimately constrict at its base, 
separates becomes an independent animal, ‘The rate of budding 
