32 Messrs Forbes and Gootlsir 07i Pelonaia, 



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 their 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 primary branches, 

 the more minute divisions following the same mode of rami- 

 fication. 



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 Ascl- 

 dice, of a ganglion situated in the substance of the mantle, be- 

 tween the oral and anal orifices. It is globular, and sends off 

 nervous twigs, 1. 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 coeca, arranged ' 

 at right angles, and opening into them along each side. 

 These tubes are attached to the internal surface of the man- 

 tle, their mouths free for a short distance, and prominent, the 

 rest of their extent and the attached coeca 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 towards its neighbour, and then 

 proceeds forward parallel to itself. The branchial vein runs 

 midway between the generative tubes, above, and the bran- 

 chial 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. 



Anatomy of P. corruyata. 



The structure of this species differs very little from that of 

 the P, glabra. The animal being elongated, the organs are 



