ANATOMY AND PHYSIOLOGY. 31 



cliate allies. If one of these masses were greatly elongated, 

 so as to become tubular, and if the male vesicles were increased 

 in number, their lower extremities pulled from beneath the 

 ovigerous sac and stretched out on the mantle, we should have 

 something very similar to that which subsists in Pelonaia. 



Another modification of these organs occurs in Styela varln- 

 bilis, an undescribed species related to Cynthia canopn*, 

 Savigny. In this the ovaries assume the form of distinct, 

 wide, slightly undulated tubes, of which there are two on the 

 right and two 011 the left side of the mantle, each having its 

 own short nipple-like oviduct which opens into the cloaca, 

 there being two on each side of the anus. The testis is com- 

 posed of numerous irregularly-lobulated vesicles scattered 

 over the lower portion of the mantle in the vicinity of the 

 posterior extremities of the ovaries, but with which they have 

 no connexion, each separate vesicle having its own short 

 nipple-like duct or vas deferetis. 



The reproductive organs do not exhibit any great diversity 

 in the genus Molgula, the ovary and its testis being always 

 combined, and forming one or two elongated masses, in which, 

 however, the two component elements can always be detected 

 by the aid of their colour and structure. The testis is com- 

 posed of a vast number of branched vesicles or cascal tubules, 

 crowded together and sometimes assuming a dendritic appear- 

 ance, while the ovary seems to be a lobulated sac, usually well 

 filled with eggs. 



In M. concliilega there are two such masses, placed trans- 

 versely, which are generally irregular in form, but sometimes 

 are broadly fusiform and a little arched. That 011 the right 

 side of the mantle lies upon the upper border of the intestine ; 

 the other occupies the centre of the left side of this tunic. 

 The oviducts are two short tubes ; they pass out of the ventral 

 or anterior extremitity of the mass, and open into the cloaca 

 on each side of the intestine. There are four or five long 

 nipple-like sperm-outlets, situated at a little distance from 

 each other along the body of the organ. These open directly 

 into the atrial space on either side of the branchial sac. 



A similar arrangement of the genitalia, with numerous short 

 deferent canals, has been described by Van Beneden, in his 

 Ascidia ampulloides*, which is, there can be little doubt, a 

 Molgula. There are two similar genital masses in M. simpler ; 

 but they are comparatively slender, and are pretty-regularly 



* " Eecherches sur 1'Enibryogenie, 1'Anatomie, et la Physiologie des 

 Ascidies Simples." ' Memoires de FAcademie Eoyale de Belgique/ xx (1847). 



