282 Mr. A. Hancock on a species of Hydra 
selves to great advantage. They are now seen to be very variable in 
form, Pl. VI. figs. 3, 4,—or rather that they have great command 
over it, contracting themselves until they are almost globular or 
vase-like, with the tentacles very short and swelled out in the 
centre ; then, extending themselves, they become linear, much at- 
tenuated, 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 Hydre must be nearly in total darkness ; but on bemg 
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 number by gemmation, the buds sprouting from the 
lower portion of the body,—rarely more than one at a time. 
Afterwards the budding was much less frequent ; and in about 
a month from the time they were taken, most of the specimens 
had perished. Two or three, figs. 1 & 2, more favourably placed 
than the rest, continued to live on for some time longer, and 
thrived well; but they changed considerably in appearance. <A 
short way below the tentacles two tubercles, a, a, had developed 
themselves opposite to each other, and were in every respect 
symmetrical; and the body was considerably enlarged towards 
the lower extremity. In this state the animal had a pedunculate 
appearance, and I was quite at a loss to account for the change. 
These specimens belonged to the first batch procured in Bromley 
Lough. On visiting the lakes again, however, in September, and 
getting a fresh supply, nearly all the individuals exhibited the 
same appearances ; the tubercles being invariably a little below 
the tentacles, though not always symmetrically placed ; and oc- 
casionally they were three and even four in number : the swelling, 
too, on the lower part of the body varied in different specimens. 
