POLYZOA. 9/ 



organ is appended, in place of the internal branchial &ac of 

 the compound Ascidiae. These last (the compound Ascidiae) 

 on a general view, having a lobed or valvular opening, 

 leading to a capacious branchial cavity or sac, over the pa- 

 rieties of which the branchia are distributed ; at the bottom 

 of this cavity is found the real mouth of the animal, leading 

 through a gullet more or less long to the stomach, which 

 is thick and muscular ; from the lower end of this, the 

 intestine issues and shortly bending upwards, terminates 

 near the front of the branchial opening ; the ovarium is 

 either situated in the fold formed by the intestine on one 

 or both sides of the animal, or is appended to the lower part 

 cf the fold, and sends its oviduct upwards along the course 

 of the rectum ; all these parts are included within a com- 

 mon or exterior tunic, whether the individuals are simple 

 Gr compound. 



The other species of Sertularia in which the animals have 

 been determined to be Polyzose, may, together with Sertu- 

 laria imbricata of Adams, perhaps, be referred to one Genus, 

 although they differ remarkably in habit, in the arrangement 

 of the vesicles, and even in the number of tentacula, which 

 vary from eight to ten, being in Sertularia Pustulosa, 

 Spinosa and Cuscuta 8, in S. imbricata 10. To this Genus 

 the name of Vesicularia may not be thought inapplicable, 

 and as the individuals which compose it have been hitherto 

 very imperfectly understood, a short description of each, 

 illustrated by magnified figures, must prove satisfactory to 

 the Zoological Student. 



Fesicularia Cuscuta (Sertularia of authors,) (PI. II. f. 1.) 

 bears some slight resemblance to V. imbricata before des- 

 cribed, in the flaccidity of its branches, and the irregular 

 distribution of its vesicles, these however on close exami- 

 nation are found to be much fewer in number and much 

 more scattered, at the same time that the whole is infinitely 

 smaller, being indeed the most delicate species known, 



