282 Mr. A. Hancock on a species of Hydra 



selves to great advantage. They are now seen to be very variable in 

 form, PI. 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 Hydra 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 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. 



