414 Proceedings of the British Association. 



But as if the purposes exacted by the existence of the latter were 

 now fulfilled, it dies while the existence of the second has scarcely 

 attained maturity, and as a third cell, beside the second, is form- 

 ing for a basis to further incerment. 



All the preceding- inhabit the sea, and propagate though solitary. 



6. The Cristatella mirabilis, an inhabitant of the fresh waters of 

 Scotland, is the most remarkable of polypiferous products, and per- 

 haps it should constitute the type of a distinct genus. Specimens 

 are of a longer or shorter oval figure, flattened, extending from six 

 to twenty-four lines in length, by two or three in breadth, and re- 

 sembling the external section of an ellipsoid. The whole of the 

 under, and the middle of the upper, surface are smooth, the latter 

 environed by a triple row of 100, 200, or 300 polypi, rising from 

 within the margin. This product is of a fine green colour, and soft 

 fleshy consistence. 



Each polypus, though an integral portion of the common mass, 

 and incorporated with it, is a distinct animal, endowed of itself with 

 individual sensation and action. It consists of a fleshy stem issuing 

 from the mass, crowned by a head like a horse-shoe, which is bor- 

 dered by about 100 tentacula. Floating particles attracted by the 

 mouth are conveyed into the stomach and intestinal organ, which 

 are exposed within the body The common mass enjoys the facul- 

 ty of very slow locomotion, either extremity indifferently being in 

 advance ; and thus are 300 animals or more subjected to its voli- 

 tion, by bearing along the whole in progression. 



On dividing a specimen asunder, each portion receded, as if by 

 mutual consent. 



Twenty, thirty, or more, lenticular substances, imbedded in the 

 flesh, are exposed through the translucent green of the animal, 

 which may escape while it is vigorous, but which are liberated to 

 float on the water toward the end of autumn, by its decay and de- 

 composition. These are ova with a hard shell, and yellowish fluid 

 contents. Their surface is browp, and the circumference yellow, 

 begirt by a row of projecting double hooks. 



In five or six months, one side of the liberated substance gapes 

 as an oyster-shell to protrude an originating polypus, which, by a 

 remarkable provision of Nature, floats with the head downwards, 

 for absorbing the aliment below. When it is enabled to aflix itself 

 on quitting the g^^, a second polypus appears beside the first, then 

 a third, and thus of others, while the common base remains dispro- 

 portionately large. Perhaps the earlier perfect formation is as a 



