42 ANATOMY AND PAVSIOLOGY OF SALPA AND PYROSOMA 



too exclusively, as there can be little doubt that the whole respiratory- 

 cavity performs the branchial function. It is proposed, therefore, ta 

 call it the Iiypopharyngcal band, on the supposition that the proper 

 respiratory cavity of the Ascidians answers to an enlarged pharynx. 



11. The muscular bands {k) are closely adherent to the inner tunic ; 

 they are composed of flattened fibrils, about titV uth of an inch in 

 diameter, which are verj' distinctly transversely striated, the striae 

 being about foVo-th of an inch apart. The bands appear to possess 

 no sarcolemma. 



12. The intestinal canal (Plate XV. [Plate s] figs. 5 and 6) com- 

 mences by a wide somewhat quadrangular mouth (r) opening into 

 a flattened cesophagus, and placed at the re-entering angle formed 

 by the hj-popharyngeal band and the upper wall of the respiratory 

 cavity. The intestine passes backwards, then becomes suddenly bent 

 upwards upon itself, and curving slightly to the right, terminates 

 in a wide flattened anus, close above and to the right side of the 

 mouth is). 



A wide ca;cal sac (/), given off on the left side of the intestine and 

 bending upwards and to the right side, constitutes the stomach. 



13. There is a very peculiar appendage to the intestinal canal 

 hitherto, it is believed, quite undescribed, and consisting of a system 

 of delicate, transparent, colourless tubes, with clear contents, arising 

 by a single stem from the upper part of the stomachal cjecum, and 

 thence ramifying over the surface of the intestine (5, 6, u), on what 

 may be called the rectum, that is, the terminal portion of the intestine \ 

 it forms a sort of expansion of parallel anastomosing vessels, which 

 all terminate at the same distance from the anus anteriorly, and from 

 the bend of the intestine posteriorly, either by uniting with one 

 another or in small pyriform cjeca, Plate XV. [Plate 5] figs. 5 and 6. 



Do these represent a hepatic organ, or are they not more probably 

 a sort of rudimentary lacteal system, a means of straining off the 

 nutritive juices from the stomach into the blood by which these 

 vessels are bathed ? 



The intestine is connected with the parietes of the sinus in which 

 it lies by innumerable delicate short threads, like a fine areolar tissue. 



14. In Salpa A, the only other organ contained in the circum- 

 visceral sinus, besides the intestine and " system of tubes," is a mass 

 of clear cells ((^), rendered polygonal by mutual pressure, and placed 

 at the upper and back part of the sinus ; to this body the name of 

 " eljeoblast " has been given by Krohn. It has by some authors been 

 confounded with a liver, an organ to which it certainly has no analogy 

 whatever. The elaeoblast is much larger and more conspicuous in the 



