264 MALPHIGIAN BODIES. 



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

 distinctness I could desire) in surface views of the embr37onic 

 kidney of stage Q. The condition of the Wolffian body re- 

 jyresented on PI. XIX. fig. 5 renders it prohalle that the accessory 

 Malpighian body in each segment is developed in connection 

 ivith the anterior growth from the original vesicle at the end of 

 the segmental tube of the succeeding segment. How the third or 

 fourth accessory Malpighian bodies, when present, take their 

 origin I have not made out. It is, however, fairly certain that 

 they form the commencement 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 second- 

 ary connection between the segmental tube and the pre- 

 ceding segment may explain a peculiar observation of Dr 

 SpengeP 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 de- 

 scribed, though without the development of a secondary Mal- 

 pighian body, have been developed? In my embryos the 

 secondary coil of the segmental tubes opens, as in the Anura, 

 into the fourth section of a kidney tubulus. 



Development of the Milllerian and Wolffian ducts. 



The formation of the Miillerian 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 

 which I differ from him. These are for the most part of a 



1 Loc. cit. pp. 85—89. 



