134 ANTHOZOA HYDROIDA. 



from the body, lie during the winter in a quiescent state, and are 

 stimulated to evolution not until the return of spring and its genial 

 weather. Few observations have been made on these ova ; so that 

 their structure, their source, their manner of escape from the body, 

 and their condition during winter, are scarcely known. Trembley 

 describes them as little spherical excrescences, of a white or yellow 

 colour, attached to the body by a very short pedicle. He never saw 

 more than three on the same polype. After some time they became 

 separate, and fell to the bottom of the glass of water in which the 

 creatures were kept, where they came to nothing, excepting one 

 only, which was presumed to have evolved into a polype ; for 

 although his experiment renders this conclusion probable, it was 

 still rather an inference than an actual observation so much so, that 

 Trembley continued to entertain doubts of their nature. Jussieu, it 

 seems, conceived that each little excrescence was a vesicle filled with 

 minute ovules ; and Ehrenberg's opinion differs from this merely 

 in the mode of expression, for he calls the deciduous autumnal bud, 

 (which, he says, has no tentacula, and is loaded with ova,) a female 

 or hermaphrodite polype. 



It appears that Ehrenberg and Dujardin have described and 

 figured the ova of the Hydrse as being spinous, but M. Laurent has 

 never found them to be so. According to this naturalist, when a 

 Hydra has laid its ovules, it gradually lowers itself and covers them 

 with the half of its body ; which, spreading out and thinning pro- 

 portionably, passes into the condition of a horny substance, that 

 glues to plants and other substances the eggs disposed in a circular 

 manner around the mother. She ends her course by dying in the 

 midst of these ova. M. Laurent has procured eggs from the in- 

 dividuals of three successive generations ; that is, from a mother, 

 from her eldest progeny, and from her youngest, and from her 

 grand- children ; all of which died in the manner described after 

 having laid their eggs.* 



These are the modes in which the Hydra naturally multiplies its 

 kind ; but it can be increased, as already hinted, by artificial sections 

 of the body, in the same manner that a perennial plant can be by 

 slips and shoots. If the body is halved in any direction, each half 

 in a short time grows up a perfect Hydra ; if it is cut into four or 

 eight, or even minced into forty pieces, t each continues alive, and 



* L'Institut, no. 465, Nov. 1842, p. 416. 



f " J'ai ouvert sur ma main un polype, je 1'ai etendu, et j'ai coupe en tout sens la 

 peau simple qu'il formoit, je 1'ai reduit en petits morceaux, je 1'ai en quelque maniere 



