OF A SILUROID; S. HIROTA. 375 



arise at the same level from tlie dorsal aorta beliind the first hœmal 

 arch (Fig, 10). Their com-ses may vary more or less in different 

 individuals : hoth of them may run in behind (as is represented 

 in Fio". 10), or before, the coalesced apophyses of the second caudal 

 vertebra or one of them may pass before, and the other behind, the 

 same apophyses. They may send oiï small Ijranches before entering 

 the stalk of the appendage. In all the cases I have examined, I have 

 found them symmetrically paired in the basal portion of the stalk 

 (Fig. 13). As they proceed centrifugally, they divide and subdivide 

 in the usual manner, until they end in capillaries forming the net- 

 work around the pits of the lobes. 



The venous vessels which arise from the capillaries become 

 gradually larger as they proceed centripetally by the union of smaller 

 vessels. In the distal portion of the stalk (Figs. 14 and 15), they are 

 alreadv united into two main trunks, each coming from the cor- 

 responding half of the appendage. Sooner or later before entering the 

 body proper, these two are also fused into one (Fig, 13), In the body 

 proper it passes behind or before the ventral apophyses of the second 

 caudal vertebra and opens into the cardinal vein at tdDout the level 

 of the origin of the arteries (Fig. 10), and in company with a pair of 

 veins^ comina' from the abdominal wall on both sides. Fiofs, 13-16 

 represent selected transverse sections of the stalk between its base where 

 it is attached to the urogenital papilla and the point where it divides 

 into two, and Fig. 17 is a horizontal section cut through the plane 

 indicated by the letter (a) in F"ig. 3. In such transverse sections, it 

 is natural that some of the blood vessels should Ije cut obliquely or 

 one and the same vessel should appear two or three times in one 

 section on account of its beinçr- bent or curved in its course. But in 

 spite of these circumstances it is clear from these figures that all the 

 larger vessels belong to the venous system and are monstrously large 



