258 SELIG HECHT 
4. Ascidia maintains a seawater current of large volume and 
low pressure. The volume of the water moved per unit weight 
decreases as the size of the animal increases. The difference in 
intensity and direction between the incoming and outgoing 
currents enables Ascidia to secure a continuous supply of fresh 
seawater independent of the movements of the sea. 
5. Food collection is accomplished in the branchial sac with 
the aid of the papillae and the mucus secreted by the endostyle. 
The food particles are transported in a mass across the face of 
the branchial sac, dorsally and posteriorly into the oesophagus. 
6. Ascidia cannot survive solely on the dissolved organic 
contents of the seawater. It must be furnished the suspended 
contents as well. | 
7. The species is capable of three kinds of movement: the 
siphon rims can close and open, the body can contract along the 
dorso-ventral axis, and the entire animal can bend toward its 
base of attachment. The movements are accomplished by 
several sets of smooth muscle, which depend for their proper 
action on the function of the test as an exoskeleton. 
8. Ascidia performs rhythmic movements to discharge the 
contents of the branchial sac. No function can be ascribed to 
this rhythmic occurrence, and a suggestion is made that it may 
represent the degenerate remains of an activity homologous with 
the rhythmic pulsation of the salpas. 
VI. BIBLIOGRAPHY 
Cautuery, M. 1895 Contributions a l’étude des ascidies composées. ‘Bull. 
sci. France et Belg., T. 27, p. 1-158. 
Crozier, W. J. 1916 Some indicators from animal tissues. Jour. Biol. Chem., 
vol. 24, p. 443-445. 
Cuénor, L. 1891 Etudes sur le sang et les glandes lymphatiques dans la série 
animale. Arch. Zool. Expér., Sér. 2, T. 9, p. 13-90. 
Dexace, Y., ET Hfrovarp, E. 1898 Les Procordés. Traite de Zoologie 
concréte, T. 8, 379 pp. 
For, A. 1908 Note sur la régénération de la tunique chez les Tuniciers. Bull. 
Soc. Zool. France, T. 33, p. 79-81. 
Hecut, 8S. 1916 The water current produced by Ascidia atra Lesueur. Jour. 
Exp. Zodl., vol. 20, p. 429-434. 
