144 ZOOPHYTES. 



eye, now exhibited six vivid red specks around each of the low serrated ori- 

 fices. An internal blood-vessel below collapsed about sixty times in a 

 minute, and dark particles, intermixed with its fluid contents, were evi- 

 dently conveyed by other channels to different parts of the body ; while in 

 some portions of the transit, they were carried along with accelerated velo- 

 city. Circulation continued visible during a fortnight. As the animal 

 darkens with age, nor has any means of relieving its skin from the extra- 

 neous matter always deposited from sea-water, the lower portion of the 

 body, wherein the blood-vessel is the best exposed, gradually becomes ob- 

 scured. Here the marginal specks remained visible also, until similar ob- 

 scuration rendered them imperceptible. 



Such minute specimens grow rapidly, but they can be seldom pre- 

 served long. 



The Ascidia rustica is occasionally found in numerous societies, but for 

 the most part it is solitary, or only a few are together. Above twenty 

 were seated on one of the valves of the razor shell (Sokn siliqua) ; about 

 eighty invested another shell, crowded within an area not exceeding twenty- 

 one lines square, where no space seemed remaining for further increment. 

 A colony sometimes forms a kind of belt around the circumference of a 

 shell, whereon the Ascidise have originated, or a group is concentrated in 

 the middle only. — Fig. 6. 



The brood is seen in remarkable profusion, and absolutely compressed 

 within such limits as might be concluded pernicious to the individuals. 

 Of this there is an example of the young of the Ascidia rustica, as I con- 

 ceive, which is represented by Plate XXXV. Here two slender portions 

 of a marine vegetable production, one of the Floridice, were each invested 

 by about 100 small Ascidia;. The whole subject resembled two strings, 

 three inches long, entirely beset with animals like currants on their twig. 

 From its appearance, it might have been almost compared to some of the 

 Botryllus, among the compound Ascidise. 



Individually the animals were grey. Many had a white cross on the 

 skin, which appeared to be composed of minute pure white specks under 

 the microscope. 



This specimen having been suspended by a silk thread, in a capacious 



