518 THE ANATOMY OF INVERTEBRATED ANIMALS. 



the Botryllidm^ however, the stomach is bent at right angles 

 upon the gullet, as in Appendicular la ; the intestine almost 

 iiumediately turns forward, and then, turning sharply upon 

 itself, passes forward parallel with the hinder part of the 

 branchial sac, on one side of which it opens into the atrium. 



A similar arrangement obtains in Perojyhora., but the 

 branchial sac extends backward for a short distance on one 

 side of the stomach. In the solitary Ascidians the stomach 

 lies sometimes altogether behind the branchial sac {Pelonala^ 

 some PhallasltB) ; but, usually, the branchial sac extends so 

 far back that the whole alimentary canal lies on one, usually 

 the right, side of it. In Phallusla monachufi^ the hinder end 

 of the branchial sac is recurved, and the oesophageal opening 

 looks backward to the fundus of the sac, instead of forward 

 to the mouth. 



In many Ascidians a strong fold of the endoderm of the 

 intestine projects into its interior, as in Lamellibranchs and 

 in the Earthworm, where such a fold constitutes the so-called 

 typhlosoU. 



In the pelagic Tanicates, S'dpa^ Pi/rosoma^ and Pollolwn, 

 I found a sj'stem of fine tubules ^ which ramify over the in- 

 testine and are eventually gathered together into a duct which 

 terminates in the stomach. An apparatus of the same nature 

 exists in Phallusla, Cynthia, Molgida, Perophora, Potrylliis, 

 PotrylloldeSy ClaveUna, Aplldum, and Dldemnum,^ and I 

 have little doubt that it is hepatic in its function. In some 

 Oj/nthke, however, there is a follicular liver of the ordinary 

 character, which opens into the stomach by several ducts. 



In some Phallitslce, the alimentary canal is coated by a 

 very peculiar tissue, consisting of innumerable spherical sacs 

 containing a yellow concretionary matter. In Molgula (and 

 in the A^cldla vltrea of Van Beneden) an oval sac containing 

 concretions lies close to the genital gland, on one side of the 

 body. As these concretions have been shown by Kupfer ' to 

 contain uric acid, the organ must be regarded as renal in 



' Saviijnv seems first to have observed this organ, as wonlcl appear from his 

 account of Diazoaa (" Momoires sur les Animanx sans vertebres," p. 176). and 

 the description of Plato 12. Lister mentions and figures it in FeropJiora (" Phil. 

 Trans. '• 1834). 



2 " Reports of the British Association," 1852. Hancock, " On the Anatomy 

 and Physiology of tlie Tunicatay ("Journal of the Linnaean Society," vol. ix.) 

 The development of these tubules from the stomach was traced by Krohn in 

 PhaUusia, and by mvself in Pi/ro^oma. 



3 " Zur Entwickeluug dor einfachcn Ascidien." (" Ai'chiv fiir Mikr. Ana- 

 tomic," 1872.) 



