SERTULARIA. 205 



the peculiar mode whereby the race is carried on, may prove of great as- 

 sistance. Little difficulty is experienced here, among the higher depart- 

 ments of zoology, but on descending to the lower, the subject becomes 

 more obscure. 



In considering the two products before us, we find the red Serftdarid 

 antennina rising by a single stem, clothed with innumerable slender twigs, 

 issuing immediately from it, that it bears ovate vesicles set in the axilla 

 formed by the twigs with the stem, each producing a single very large 

 planula : and that the entire specimen may be contained in a cylinder ten 

 inches high, and of eight lines in diameter. 



On the other hand, contrasting the green Sertularia (antennina) 

 ramosa, we find the adult always consisting of a number of subordinate 

 parts ; first boughs originating from the stem, then branches profusely 

 clothed like the other with twigs, but never occurring, to me at least, 

 nearly of equal height, nor bearing similar vesicles exclusively on the sub- 

 ordinate parts. 



In very luxuriant specimens of the latter, that is the green, there are 

 interspersed among the various parts, long slender twigs or branches, bor- 

 dered on each side by the finest, most delicate hairs with cells and hydrse ; 

 and bearing long ampullate vesicles. — PI. XXXVIII. fig. 9. 



The last are frequently in vast profusion ; sometimes pure white, some- 

 times reddish, according to the nature of their contents. These vesicles 

 do not in the least resemble the ovate form just described. But consider- 

 able difference appears in the length and obliquity of the neck, as well as 

 in the colour, of those of different specimens. 



Such are the vesicles usually occurring on the Nemertesia or Sertularia 

 ramosa of Plate XL. But to comprehend the subject sufficiently, would 

 almost require ocular inspection of the original, for description is not to be 

 conveyed in words. 



On the 29th of October, the contents of some prolific vesicles, which 

 had been set apart two days preceding, were found in various progressive 

 stages, and presenting obvious diversity of appearance. Minute spherules 

 or spherical triangular prisms were among them. 



Life became evident in the contents of several vesicles now subjected 



