PELONAIAD^. 45 



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 respiratory sac, opposite to 

 the branchial vein, performs the functions of a branchial artery. It 

 is interesting to observe here the differences between the modes in 

 which the branches enter the branchial vein, and strike off from 

 the branchial artery. In the former, just before the branches 

 enter the trunk, they give off a number of vessels, which enter 

 the trunk alongside of the parent trunk, the combination forming 

 a sort of delta : in the latter they leave the trunk singly, and send 

 off their branches in a radiating direction. At a little distance 

 from the trunks of both artery and vein, the secondary branches 

 become parallel to one another, and perpendicular to their pri- 

 mary branches, the more minute divisions following the same 

 mode of ramification. 



" Not having examined the animal when alive, we have no 

 information as to the nature of its blood. 



" 4. Nervous System. — This system consists, as in other Ascidice, 

 of a ganglion situated in the substance of the mantle, between the 

 oral and anal orifices. It is globular, and sends off nervous twigs, 

 I. to the respiratory orifice of the mantle ; 2. to the respiratory 

 sac, where it begins to exhibit the transverse plaits ; and, 3, to 

 the anal orifice of the mantle. 



" 5. Generative System. — The generative organs consist of two 

 elongated tubes, closed at one end, open at the other, and having 

 a great number of close-set parallel ca^ca arranged at right angles, 

 and opening into them along each side. These tubes are attached 

 to the internal surface of the mantle ; their mouths are free for a 

 short distance, and prominent, the rest of their extent and the at- 

 tached c£eca adherent. The orifices of these organs are situate at 

 the junction of the first with the second quarter of the animal, 

 and one third of the other end of each turns in toward its neigh- 

 bour, and then proceeds forward parallel to itself The branchial 

 vein runs midway between the generative tubes above, and the 

 branchial artery in a corresponding course below, so that the 

 threads of attachment of the plaits on the external surface of the 

 sac are fixed into the tubes in a series on each side. 



