Morse.] 352 [October 18, 



Good sir called attention to the resemblance between the phryangeal 

 sac of the Ascidians, and that of Amphioxus. 1 He says "The Lance- 

 let respires by receiving sea Avater into the anterior compartment 

 of the intestinal tube — this cavity is kept dilated by the elasticity of 

 the numerous filamentous ribs, and this dilatation may be increased 

 by the action of the super-imposed ventral bandies of the lateral 

 muscles. It is contracted by the action of the abdominal muscle. 

 This is a mode of respiration similar to that which prevails in the 

 tunicated mollusks. It is interesting to observe that the branchial 

 membrane of the Lancelet is exactly similar in its peculiar vascular- 

 ity (ramifications at right angles) to that which lines the branchial 

 cavity of the mollusks just specified. . ». . . As in Ascidiae the 

 entrance of the intestino-respiratory canal is guarded by filaments." 



In the recent removal of the Tunicates from the Mollusca, and 

 incorporation of the same with the Vermes by Gegenbaur and others, 

 it is interesting to recall from the memoir of Goodsir above cited, the 

 fact that he calls attention to certain resemblances between Amphi- 

 oxus and the Annulosa. 



"The plan of circulation is simple and in accordance with the 

 primitive condition of the respiratory apparatus, both functions beino- 

 performed in a manner closely resembling that observed in certain 

 annulose animals. The dorsal vessel corresponding to the heart, or 

 branchial artery, and the abdominal vessel to the aorta of the Lance- 

 let." Ibid., p. 260. 



Any scrap of information connected with a subject so profoundly 

 interesting justifies me in bringing forward a single observation 

 made upon the young stages of a sessile Ascidian, Cynthia piriformis, 

 at Eastport, Maine, July, 1870. 



John E. Gavit, Esq., of New York, kindly placed the larva? in my 

 hands for examination. The eggs were noticed in all stages, as well 

 as free swimming larvse in active motion. These were easily seen 

 with the unassisted eye and looked like gigantic spermatozoa. A 

 special series of observations in another line limited me to a single 

 examination of these interesting forms. 



Kowalevsky in the paper above referred to represents on plate n, 

 fig. 26, a delicate membrane bordering the tail like a fin. This is 

 represented as structureless. In the unfolded tail no traces of cartil- 

 agenous centra are shown, though he represents these parts as more 



1 Goodsir on the Anatomy of Amphioxus. Royal Society of Edinburg, Vol. xv, 

 part I, page 259. 



