482 DEVELOPMENT OF ELASMOBRANCH FISHES. 



immediately behind the opening of the Wolffian duct (so far as 

 could be determined), by four apertures on each side. In a 

 section made through the part of the wall of the cloaca con- 

 taining the openings of the ureters of both sides, there were 

 present on the left side (where the section passed nearer to the 

 surface than on the right) four small openings posteriorly, viz. 

 the openings of the ureters and one larger one anteriorly, viz. 

 the opening of the Wolffian duct. On the other side of the 

 section where the level was rather deeper, there were five dis- 

 tinct ducts cut through, one of which was almost on the point of 

 dividing into two. This second section proves that, in this in- 

 stance at least, the two ureters did not unite till just before 

 opening into the urinogenital cloaca. The same section also 

 appeared to shew that one of the ureters fell not into the cloaca 

 but into the Wolffian duct. 



As stated above both the Wolffian duct and the ureters fall 

 into an unpaired urinogenital cloaca. This cloaca communicates 

 at one end with the general cloaca by a single aperture situated 

 at the point of a somewhat conspicuous papilla, just behind the 

 anus (PI. 20, fig. i, o), and on the other it opens freely into a 

 pair of bladders, situated in close contact with each other, on 

 the ventral side of the kidney (PI. 20, fig. I, sb}. To these 

 bladders Professor Semper has given the name uterus mascu- 

 linus, from having supposed them to correspond with the lower 

 part of the oviducts of the female. This homology he now 

 admits to be erroneous, and it will accordingly be better to drop 

 the name uterus masculinus, for which may be substituted 

 seminal bladder a name which suits their function, since they 

 are usually filled with semen at the generation season. The 

 seminal bladders communicate with the urinogenital cloaca by 

 wide openings, and it is on the borders of these openings that 

 the mouths of the Wolffian duct and ureters must be looked for. 

 My embryological investigations, though they have not been 

 specially directed to this point, seem to shew that the seminal 

 bladders do not arise during embryonic life, and are still absent 

 in very young individuals. It seems probable that both the 

 bladders and the urinogenital cloaca are products of the lower 

 extremities of the Wolffian duct. The only other duct requiring 

 any notice in the male is the rudimentary oviduct. As was first 



