406 MR. HANCOCK ON A SPECIES OF HYDRA, 
they do not exactly agree with any of the known forms, though 
they come very near to H. fusca, of which they may probably 
prove to be a variety. 
On removing from the water, a stone to which these Hydre are 
attached, they appear as irregular, minute depressed globules of 
gelatine, of a pale red flesh-colour, dispersed over the surface, 
sometimes in great numbers on one stone, but never crowded on 
each other. When placed in a bottle of water, they soon become 
fixed to its sides, and spreading out their tentacles, display them- 
seves to great advantage. They are now seen to be very variable 
in form, Pl. VII. figs. 3, 4,—or rather that they have great com- 
mand over it, contracting themselves until they are almost globu- 
lar or vase-like, with the tentacles very short and swelled out in 
the centre ; then extending themselves, they become linear, much 
attenuated, and frequently half an inch long,—the tentacles, fig. 5, 
being very delicate, and tapering imperceptibly towards the ex- 
tremity, which is enlarged and rounded, forming a nodule or bulb 
of no great size, but quite visible to the naked eye. The polype, 
however, is usually much less extended, and is generally a little 
bulged in the centre ; the tentacles are then somewhat longer 
than the body, but are shorter than it when the animal is fully 
stretched out. There are usually six tentacles, occasionally five, 
rarely seven ; they are white, never coloured in the centre like 
the body, which, as already stated, is a red flesh-colour ; it is also 
sometimes yellowish. The colouring, which is apparently much 
affected by exposure to light, depends on the granules that line 
the internal or digestive cavity, and is most intense near the 
mouth. 
When in their native haunts, attached to the under side of 
stones, the Zydrc must be nearly in total darkness; but on being 
placed in a bottle, they become exposed to the solar rays, and in 
the course of a few days, are almost completely bleached. Sup- 
posing that this loss of colour was occasioned by the want of food, 
the specimens were supplied with animalcules ; but their original 
hue was not in the least restored. 
During the first week or ten days, the captives added greatly 
to their numbers, by gemmation, the buds sprouting from the 
