494 DEVELOPMENT OF ELASMOBRANCH FISHES. 



have been able to trace it (though not with the distinctness I 

 could desire) in surface views of the embryonic kidney of 

 stage Q. The condition of the VVolffian body represented on 

 PL 20, fig. 5 renders it probable that the accessory MalpigJiian 

 body in each segment is developed in connection until the anterior 

 growth from the original vesicle at the end of the segmental tube of 

 the succeeding segment. How the third or fourth accessory Mal- 

 pighian bodies, when present, take their origin I have not made 

 out. It is, however, fairly certain that they form the com- 

 mencement of two additional coils which unite, like the coil 

 connected with the first accessory Malpighian body, with the 

 collecting tube of the primitive coil close to its opening into the 

 Wolffian duct or ureter. 



The connection above described between two successive 

 kidney segments appears to have escaped Professor Semper's 

 notice, though I fancy that the peculiar vesicle he describes, 

 loc. cit. p. 303, as connected with the end of each segmental 

 tube, is in some way related to it. It seems possible that the . 

 secondary connection between the segmental tube and the pre- 

 ceding segment may explain a peculiar observation of Dr 

 Spengel 1 on the kidney of the tailless Amphibians. He finds 

 that, in this group, the segmental tubes do not open into Mal- 

 pighian bodies, but into the fourth division of the kidney tube. 

 Is it not just possible that in this case the primitive attachment 

 of the segmental tubes may have become lost, and a secondary 

 attachment, equivalent to that above described, though without 

 the development of a secondary Malpighian body, have been 

 developed ? In my embryos the secondary coil of the seg- 

 mental tubes opens, as in the Anura, into the fourth section of a 

 kidney tubulus. 



Development of the Mnllerian and Wolffian ducts. 



The formation of the Mullerian and Wolffian ducts out of 

 the original segmental duct has been dealt with in a masterly 

 manner by Professor Semper, but though I give my entire 

 assent to his general conclusions, yet there are a few points on 



1 Loc. cit. pp. 85-89. 



