DEVELOPMENT OF ELASMOBRANCH FISHES. 259 



eleven ureters opening into the Wolffian duct by seven distinct 

 openings. In the remaining parts of the excretory organs the 

 two species of Scyllium resemble each other very closely. 



As may be gathered from Prof. Semper's monograph, the 

 excretory organs of Scyllium canicula are fairly typical for Elas- 

 mobranchs generally. The division into kidney and Wolffian 

 body is universal. The segmental openings may be more 

 numerous and larger, e.g. Acanthias and Squatina, or absent in 

 the adult, e.g. Mustelus and Raja. Bladder-like swellings 

 of the Wolffian duct in the female appear to be exceptional, 

 and seminal bladders are not always present. The variations 

 in the ureters and their openings are considerable, and in 

 some cases all the ureters are stated to fall into a single duct, 

 which may be spoken of as the ureter par excellence ^ with 

 the same relations to the kidneys as the Wolffian duct bears 

 to the Wolffian body. In some cases Malpighian corpuscles 

 are completely absent in the Wolffian body, e.g. Raja. 



The vasa efiferentia of the testes in Scyllium are very 

 typical, but there are some forms in which they are more 

 numerous as well as others in which they are less so. Per- 

 haps the vasa efiferentia are seen in their most typical form 

 in Centrina as described and figured (PI. xxi.) by Professor 

 Semper, or in Squatina vulgaris, as I find it, and have repre- 

 sented it on PL XIX. fig. 8. From my figure, representino- 

 the anterior part of the Wolffian body of a nearly ripe embryo, 

 it will be seen that there are five vasa efiferentia (y. e) con- 

 nected on the one hand with a longitudinal canal at the base 

 of the testes (ji. t) and on the other wath a longitudinal canal in 

 the Wolffian body. Connected with the second longitudinal canal 

 are four Malpighian bodies, three of them stalked and one sessile ; 

 from which again proceed tubes forming the commencements 

 of the coils of the anterior segments of the Wolffian body. 

 These Malpighian bodies are clearly my primary Malpighian 

 bodies, but there are in Squatina, even in the generative seg- 

 ments, secondary Malpighian bodies. What Semper has described 



^ I feel considerable hesitation in accepting Semper's descriptions of the 

 nreters and their openings. It has been shewn above that for Scyllium his 

 statements are probably inaccurate, and in other instances, e.g. Eaja, I caunot 

 bring my dissoctiona to harmoaiso with his descriptions. 



