ANTHOZOA ASTEROIDA. 147 



is a free communication between these parts through the me- 

 dium of numerous minute apertures perforated in tlie sides of 

 the abdominal cavity.* It is in this tenuous inner tunic that 

 the buds or gemmse, by whose increase and evolution the 

 polype-mass is enlarged, are generated, the shape and size of 

 the mass depending upon the manner, or pre-ordained fashion, 

 in which the buds are evolved ; for in some, as in Pennatula, 

 determinate spots only have the appropriated organization ; 

 while in others, as in Alcyonium, the generative faculty ap- 

 pears to be undefined and diffused. These buds are produced 

 in the net- work of the crust ; while the true ova, by which 

 the species is propagated, always germinate from the inner 

 surface of the lining of the canal that is prolonged into the 

 common mass from underneath the abdominal cavity of the 

 polype, and consequently in immediate communication with it. 

 In Pennatulidae we first detect the ova between the mem- 

 branes of the polypiferous pinna ; in Alcyonium in the carti- 

 laginous canals which are traced through the polype-mass ; 

 and, in Gorgonia, Mr. Couch has shewn that their position is 

 the same, in opposition to the assertion of Cavolini, who in- 

 forms us that they germinate in eight distinct " ovaria at the 

 base of each polypus." They first appear like a minute 

 smooth wart, which gradually rises up from the surface, en- 

 larging itself at the same time, and, when a certain size has 

 been attained, the wart becomes constricted at its base, then 

 shortly pedicelled, and at last it separates a free egg by the 

 absorption of this retaining neck or umbilical cord. (Plate 

 xxxiv. Fig. 6.) The eggs, now at liberty to move, gradually 

 approach the base of the stomach, which, as already mention- 

 ed, is perforated with an opening that can be made wider, or 

 closed by means of its sphincter muscle. After several ap- 

 proaches and as many repulsions, the aperture at length allows 

 the egg to pass through into the stomach, whence it is ejected 

 through the mouth into the open sea. Professors Grant and 

 Milne-Edwards have witnessed this process in the Alcyonia, 

 and the former also in the Pennatula and Virgularia ; so that 

 when Cavolini tells us that the ova of the Gorgonia pass up- 

 wards " through eight small oviducts,"" and are discharged, by 



* Lam. Anim. s. Vert. ii. 465, 2de edit. Couch, Corn. Faim. iii. p. 52-3. 



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