322 Natural History of British Zoophytes. 



ed we perceive the oral aperture (d,) leading to a stomachical cavity 

 without intestine or other chylopoetick viscus. The body is somewhat 

 globular, soft and irritable ; and it is prolonged posteriorly down the 

 stalk or tube to be united with the central pulp which fills the branches 

 and stem, ^e.) so that in this manner all the polypes of the same 

 polypidom are connected together by a living thread, and constitute 

 a family whose objects and interests are identical, and whose work- 

 ings are all regulated by one harmonious instinct : 



" Unconscious, not unworthy, instruments, 



By whicli a hand invisible was rearing 



A new creation in the secret deep." 

 Or if, with Linnaeus and Cuvier, we suppose that the polypes of 

 every polypidom constitute only one body or individual, this may be 

 described as a sort of hydra divided, after the manner of a tree, into 

 many or innumerable branches, from each of which pullulate one or 

 more armed heads to capture and digest the prey that is to serve for 

 the nutriment of their common trunk. 



The reproductive gemmules of Tubularia and Coryne are generated 

 in the interior and extruded near the base of the tentacula ; but in 

 all the other genera they are produced in external vesicles, which 

 were therefore appropriately named by Ellis the ovaries, and which 

 we have already mentioned as being larger than the cells and irregu- 

 lar in their distribution. They are produced at certain seasons only, 

 most commonly in spring, and fall oif after the maturity and discharge 

 of their contents.* The number of the gemmules in each vesicle, and 

 their shape, varies in every species. In the vesicle they are con- 

 nected to a central placentular column, though there are some ex- 

 ceptions to this, and when mature they escape oiitwards by a disrup- 

 tion or fall of the lid which closes the top, being extruded in suc- 

 cession and, in some cases at leasts after intervals of some hours. 

 From the observations of Professor Grant, it appears to be proved 

 that, after their discharge, the ova move about for some time in the 

 water by the vibrations of minute cilia, but having in due course set- 

 tled on a proper site, they throw out, in the manner of a vegetable 

 seed, a root-like fibre to fix themselves, and then push up a shoot as 

 a commencement to the future polypidom. Polype- cells and polypes 

 are rapidly evolved on the sides of this shoot, and nourishment being 

 now I'eceived from an external som'ce, and circulating through the 



* So that'^Hedwig's axiom, adopted by M. Virey, " that the reproductive or- 

 gans of animals are continuous with the life of the individual, while the repro- 

 ductive organs of perennial plants, when their functions have been performed, 

 are thrown off, and replaced in the succeeding season by others," — must be re- 

 ceived with some limitations See Tiedemann's Comp. Physiology, p. 7G 



