284 LECTURE XI. 



its termination immediately beliind the advanced vent. The urinary 

 bladder is sometimes round (yfig. 72. h), sometimes oval or pyriform, 

 often bifid at its fundus or two-horned ; it is largest in those fishes, 

 as the Pleuronectidce, the Lophius, the Orthagoriscus, and the Cy- 

 clopterus, in which the air-bladder is absent. In the Callyomymus 

 the bifid urinary bladder extends the whole length of the abdomen 

 It always lies behind the rectum, generally receives the ureter or 

 ureters nearer its fundus than its cervix, and the latter is prolonged 

 usually into a prominent papilla behind the vent. The long cervix 

 vesicae in the Salmon is surrounded by a venous plexus. In the 

 Sturgeon the wide ureters extend along the outer borders of the 

 kidneys, and receive the vasa deferentia or oviducts in their course 

 towards the cloaca, where they unite into a short duct which forms 

 the common outlet of the urinary and generative products. 



The kidneys are long, narrow, but distinct from each other in 

 all the ganoid fishes and in the Lepidosiren. In the Lophius the 

 kidneys present a more compact form, and are situated wide apart, 

 far forwards in the abdomen, in depressions on either side of the 

 origins of the ' retractores palati.' The kidneys of the Plagiostomes 

 are also of a more compact form than in osseous fishes, and are 

 always distinct, and generally show a cerebi'iform convoluted or 

 lobulated exterior : the primary branches of the uriniferous tubes 

 are fewer, and their dichotomous ramifications more numerous* : 

 the ureteric trunk becomes superficial along the inner and fore-part 

 of the hinder half of each kidney ; after quitting which it dilates 

 in the Grey Shark ( Galeus) into a kind of receptacle behind each 

 oviduct or vas deferens, and communicating with its fellow near 

 the cloaca, terminates by a single urethral canal upon a kind of 

 penis or clitoris (^fig. 75. k) at the back of the anus, within a large 

 common cloaca. In the Torpedo, the ureters terminate on the 

 cloacal papilla by two distinct orifices. f In the Skate and Thorn- 

 back each ureter terminates in the neck of a short bifid bladder : 

 these open by a common urethra upon the cloacal papilla. The Lepi- 

 dosiren has a small urinary bladder situated, as in all fishes, behind 

 the rectum and in front of the oviducts : the ureters do not com- 

 municate directly with it, but terminate separately on small papillas 

 in the oviducal compartment of the cloaca. | With regard to the 

 circulation in the kidney in those fishes, as e. g. the Plagiostomes the 

 Lophius and the Lepidosiren, in which the organ is best defined, 

 the vein on the outer side of the kidney which receives blood from 



* In the Ray the diameter of the terminal branches of the tubuli uriniferi are 

 •,i:(th of an inch, that of the capillary renal arteries being fg^Qth of an Inch, 

 f cxxxiv. i xxxiii. pi. 27. 



