SALP.E. 487 



(1278.) In Ascidia grossularia, the eggs, as seen through the walls 

 of the ovary, are of a fine red colour, and are contained in separate sacs ; 

 so that the ovary when distended resembles a bunch of grapes. By 

 the side of the ovary is another series of sacculi (fig. 246, B, 6), the 

 contents of which abound with spermatozoa, intimating their identity 

 with the male apparatus above described. 



Fig. 246. 



B A 



Generative system of Cynthia ampulla. 



(1279.) Deprived as these animals are of any of the higher organs 

 of sense, and almost cut off from all relation with the external world, 

 we can look for no very great development of the nervous centres. 

 There is one ganglion, however, lodged in the substance of the mantle, 

 distinctly recognizable, situate in the space between the branchial and 

 excretory openings, from which large nerves are given off; but of other 

 details connected with the nervous system of the Tunicata little has 

 been made out. 



(1280.) In the seas of tropical latitudes, many forms of Tunicated 

 Mollusca are met with abundantly which, although allied to Ascidians in 

 the main points of their economy, present certain peculiarities of struc- 

 ture that require brief notice in this place. These, grouped by authors 

 under the general name of Salpce, are many of them so transparent 

 that their presence in a quantity of sea-water is not easily detected ; 

 and their viscera, if coloured, are readily distinguishable through their 

 translucent integument, which in texture seems to be intermediate 

 between cartilage and jelly. The body is oblong, and open at both 

 extremities, the posterior opening being very wide, and furnished with a 

 crescentic valve, so disposed that water is freely drawn into the interior 

 through this aperture, but cannot again be expelled by the same chan- 

 nel ; so that, being forced by the contractions of the body in powerful 

 gushes from the opposite end, it not only supplies the material for 

 respiration, but impels the delicate animal through the water in a back- 

 ward direction. The branchial chamber of Ascidia is consequently in 

 this case represented by a wide membranous canal, which traverses the 

 body from end to end ; but, instead of the network of vessels lining the 

 respiratory sac of Ascidians, a singular kind of branchial organ is placed 



