412 Proceedings of the British Association. 



Prominences soon indicate the evolution of tentacula, then with en- 

 larged instead of acute extremities as in adults ; as they extend the 

 nascent animal elevating itself on them as on so many feet, but 

 with the body inverted, enjoys the faculty of locomotion. Appa- 

 rently selecting a site, it reverses itself to the natural position with 

 the tentacula upwards, and is then rooted permanently by a pro- 

 minence, which is the incipient stalk, originating from the under 

 part of the head. Gradual elongation of the stalk afterwards con- 

 tinues to raise the head, and the formation of the zoophyte is per- 

 fected. 



It is obvious, therefore, that this product is primarily of animal 

 nature exclusively. 



4. The finest specimens of Sertularice resemble luxuriant shrubs 

 in miniature, with stems, boughs, branches, and twigs, with thou- 

 sands of cells and their polypi. One species, however, provisional- 

 ly designed Sertularia Uber, rises towards three feet high from the 

 root, thus infinitely exceeding the dimensions hitherto ascribed to 

 the Sertularise. Certain specimens of this and various others bear 

 vesicles or small vascular bodies, three or four times the size of the 

 cells containing white, pink, green, or yellow corpuscula, of a sphe- 

 rical form, in their earlier stages. All preceding naturalists have 

 conceived the vesicle, the ovarium, and these spherules, the ova 

 whereby Sertularise are propagated. But a long series of obser- 

 vations, greatly diversified and continued throughout many suc- 

 cessive years, has not led to this immediate result. 



The vesicle contains from one to thirty corpuscula, according to 

 species, which are spherical on the earliest recognition, through the 

 refining transparency of its sides. Their shape alters on approach- 

 ing maturity ; it elongates, becomes elliptical, next prismatic, and 

 at length each corpusculum issues as a perfect animal from the ori- 

 fice of the vesicle. Now in figure and in motion, together with the 

 exhibition of certain peculiarities, it bears much resemblance to the 

 plaiiaria. The colours are the same as were exposed by the transpa- 

 rency of the vesicle, which remains empty ; the dimensions of none 

 exceed a line in length. These animals may constitute a new ge- 

 nus, to be provisionally denominated Plaimla. Eight or ten species 

 of Sertulariae have affbrded them ; nor has any thing else been ever 

 obtained from the vesicle. 



The animal crawls very actively at first ; but in some days its 

 motion relaxes, it becomes stationary, contracts, and dies, though 

 without speedy decomposition, as is incident to the planaria. Short- 



