TRANSACTIONS OF THE SECTIONS. 603 



the identical place where the Planula perished. A short 

 spinous prolongation rising from the centre, becomes a stalk, 

 with an enlarging summit, which, forming into a cell, in a few 

 days more bursts, to display a living polypus in full activity. 



While scarcely mature, other buds are germinating along 

 with further extension of the parts, and quickly perfected as 

 so many more cells with their polypi ; and thus by progressive 

 multiplication is the entire specimen produced under its proper 

 aspect. 



Meantime the circular spot below, invariably white or yellow, 

 according to the Planula, is losing its opacity ; it breaks into 

 divisions resembling radicles, still confined within its margin, 

 and at last disappears in tenuity. 



Thus, with the precaution of selecting specimens bearing 

 prolific vesicles, — those exhibiting corpuscula to the eye, — a 

 whole forest of nascent zoophytes may be easily obtained. 



The author cannot affirm that amidst a multitude of observa- 

 tions he has ever witnessed their origin, under other conditions 

 than the presence of the Planulae, and these have been afford- 

 ed by eight or ten species of Sertularice, vegetating as para- 

 sites, or, independently, from solid foundations. 



Nevertheless, as truth is the sole purpose of scientific re- 

 search, several difficult questions must be offered for solution. 

 1. When does the vesicle originate? 2. Is it deciduous and 

 regenerated ? 3. Does it include some invisible pericarp or 

 true ovarium, containing the elements of the progeny of the 

 Sertularia ? 4. Is their maturity indicated by the presence of 

 the Planula ? 5. Does its escape by the orifice of the vesicle 

 promote their discharge? 6. Are these elements absorbed 

 by the Planula while in the vesicle, and their evolution after- 

 wards promoted by its death ? 



4. Flustra carbasea. — The genus Flustra is of more simple 

 structure, and consists of fewer parts than Sertularia. 



The Flustra carbasea rises from the root by a short flattened 

 stem, with a stout yellow margin, simply as a leaf consisting of 

 foliaceous subdivisions, free at the margin, as they are suscepti- 

 ble of enlargement. One surface is covered by cells of a shuttle, 

 or rather a slipper shape, the edges of the whole forming 

 that surface, level, not prominent. Each cell is composed of a 

 broad flattened top connected with the bottom by sides like 

 those connecting the back and belly of the violin, and there is 

 an aperture above towards one extremity for protrusion of the 

 polypus, which, affixed by the posterior part, reposes within, 

 folded as the letter S, and when active extends to display 

 about twenty-two tentacula. The leaf rises vertically, and the- 



