FOOD OF TUNICATA. 297 



Tunicata lived entirely upon vegetable organisms. The 

 contents of the stomachs of the Phallusiae, Clavelinse, and 

 Diazonas, examined by them, consisted of particles of flori- 

 deous alga?, which had probably found their way there 

 by chance, and a great quantity of microscopic plants of 

 low position in the series, species of Navicula, Frustulia, 

 Baccilaria, Closterium, &c* I think that I have also de- 

 tected the remains of entomostracous insects in the sac of 

 some Tunicata ; and Savigny, who has frequently made the 

 same observation, has found in even the compound species, 

 Crustacea of a higher order and greatly larger dimensions. 

 The latter, however, as Cuvier thinks, may have entered 

 against the will and to the prejudice of the mollusk ; 

 for he has observed the delicate texture of the viscera 

 torn and ruptured by such rude ingesta.f 



Of the Tunicata there are two families : one, Alcyoneae, 

 or the compound, in which numerous individuals, generally 

 of very small size, are united together, and, as it were, im- 

 mersed in a common somewhat gelatinous mass ; and an- 

 other, Ascidia), or the solitary, in which every individual is 

 single and separate, and of much greater magnitude. In 

 both of these families, there is a circular aperture, raised a 

 little above the surface of the common integument or sac, 

 and capable of being shut or opened, more or less widely, at 

 the pleasure of the animal. The rim of it is sometimes 

 plain, and sometimes cut into four, six, or eight equal seg- 

 ments ; and within the orifice there is, in very many of 

 them, a fringe formed of one or two rows of delicate cilia, 

 which I have observed, in the Ascidia rustica, to be in con- 



Epithemia sorcx Cymbella maculata 



Fragilaria pectinalis Gomphonema pohliaeforme 



Diatoma flosculosum Navicula hippocampus 



Meloseira sulcata Ceratoncis closterium 



jurgensii Coscinodiscus patina 



Surirella? lineatus 



Synedra lsevis eccentricus 



Cocconcis pediculus Actinocyclus undulatus 



Doryphora amphiccros Actinoptychus senarius 



Aclmanthes longipes Dictyocha gracilis 



Ann. and Mag. N. Hist. sec. 2, i. 323. 



* Forbes and Hanley, Brit. Mollusca, i. 7. 



t Mem. xx. 14 — " It would seem that the food of Ascidians consists 

 of very minute particles of organised matter ; for, although small Crustacea 

 and other animal remains have been occasionally met with in the branchial 

 chamber, nothing of this nature has been observed in the stomach itself, 

 and, as must be obvious to the reader, the oral aperture seems but 

 little adapted to the deglutition of bulky substances." — Jones's Anim. 

 Kingd. p. 372. 



