Messrs Forbes and Goodsir on Pelonaia, 31 



doubt exist in great abundance on the edges of the lozenge- 

 shaped spaces of the sac. 



The oesophagus commences by a white plicated opening at 

 the lower end, and on one side of the sac. It is curved in a 

 sigmoidal form, and exhibits longitudinal rugae through its 

 coats. Near the lower end of the mantle cavity, it terminates 

 by suddenly dilating into the stomach, which is pear-shaped, 

 and directed obliquely upwards towards the side opposite to 

 the a^sophagus. The internal surface of the stomach presents 

 longitudinal plicse, and is succeeded by the intestine, which 

 at first curves upwards, then down to the bottom of the 

 mantle cavity, up along the oesophageal side of that cavity, 

 and between its walls and the branchial artery, terminating 

 about the anterior third of the animal in a funnel-shaped 

 anus, which is cut into ten or eleven processes like the petals 

 of a flower. The first part of the intestine is white and 

 longitudinally plicated \ the rectum is dilated with attenuated 

 coats. 



3. Vascular system. The vascular system resembles that 

 of tlie true Ascidice, except that there is no heart. It consists 

 of two sets of vessels, with four sets of capillaries, a circle 

 in fact twice interrupted, once in the respiratory sac, and 

 again throughout the body. The branchial veins run. along 

 the. transverse plaits of the sac, receiving secondary and ter- 

 nary twigs at right angles. The primary branchial venous 

 branches empty themselves on each side into the branchial 

 venous trunk, which runs in the substance of the double cord 

 which coasts the superior aspect of the sac. This double cord 

 terminates in an abrupt manner anteriorly near the oral ori- 

 fice, and in a similar manner, but after becoming smaller, near 

 the orifice leading to the oesophagus. At this point the vein 

 becomes an artery, and probably sends back vessels to nourish 

 the sac. It now runs along the oesophagus, supplying the 

 stomach and intestine, and giving off* in its course branches 

 to the cloak. The veins arising from the arterial capillaries 

 of the body meet near the commencement of the oesophagus, 

 in one trunk, which passing along the inferior wall of the re- 

 spiratory sac, opposite to the branchial vein, performs the 

 function of a branchial artery. 



