Natural History of British Zoophytes. 243 



Amongst zoophytes there is no distinction of sexes, but every in- 

 dividual appears to be capable of producing reproductive buds or 

 gemmules.* For the production of these there is, in the opinion 

 of some good observers, a peculiar organ or ovarium in all the asci- 

 dian tribes, and it is certain that their gemmules are always gene- 

 rated within the polype cell. There are appropriate productive or- 

 gans also in the Helianthoida and Asteroida, in the former situated 

 between the ligamentous dissepiments which radiate from the mouth 

 to the base, between the stomach and the skin ; and in some of the 

 latter attached to the membranous dissepiments in the abdominal 

 cavity, while in others the gemmules appear to sprout from every 

 part of the abdominal cavity, and of the tube continuous with it. On 

 the contrary, there is no local generative organ in any Hydroida — 

 all are " full of reproductive life :" in the Hydra germs, similar in all 

 respects to the substance of the body, sprout indiscriminately from 

 every part of the surface ; in the Tubulariadee they pullulate from 

 underneath the tentacula where they may frequently be observed in 

 clusters, and, in both of these families, the germs are naked or unco- 

 vered. But in the extensive family which embraces the Sertularia and 

 all its subgenera, the gemmules, attached in general to a central pla- 

 centa, (which is but a continuation of the fleshy central part of the 

 stem,) are enclosed in vesicles of the same texture as the polypidom 

 itself, and neither proceed from, nor have any immediate connection 

 with, the proper body of the polype, being evolutions from the pith 

 or flexy axis which connects the polypes together, and binds the va- 

 rious heads into one whole. — Such is a brief summary of the facts 

 ascertained on this head, but it behoves me to mention that it is, to 

 a certain extent, at variance with the opinions of Professor Grant. 

 He maintains, from his numerous observations on a great variety of 

 zoophytes, that the gemmules by which these animals propagate are 

 highly organized portions of the gelatinous substance of the parent, 

 formed " in almost every known zoophyte," and not merely in the 

 Hydrazoa, as we have limited it, " by the common connecting sub- 

 stance of the animal, and not by the polypi, which appear to be only 

 the mouths or organs of digestion. In Plumularite, Sertulariae, Cam- 

 panulariee, horny Cellarise, Antennulariae, the ova are formed in ve- 



* " These corpuscules differ from true ova and seeds, which are ripened by fe- 

 cundation, inasmuch as the substance of which the new being is formed is not, 

 as ova and seeds are, enclosed in a special envelope, which is separated from 

 them at the moment of the developement of the germ, and inasmuch as the 

 formation of the new individual is owing to the entire substance of the repro- 

 ductive corpuscule. " — Tiedemann's Comp. Phy. 42. 



