250 EXCRETORY ORGANS IN THE ADULT. 



investigations by Dr Meyer' and by myself. Their older 

 literature is fully given by Professor Semper. In addition to 

 the above-cited works, there is one other paper by Dr Spengel' 

 on the Urinogenital System of Amphibians, to which reference 

 will frequently be made in the sequel, and which, though only 

 indirectly connected with the subject of this chapter, deserves 

 special mention both on account of the accuracy of the investi- 

 gations of which it forms the record, and of the novel light 

 which it throws on many of the problems of the constitution 

 of the urinogenital system of Vertebrates. 



Excretory organs and genital ducts in the adult. 



The kidneys of Scy Ilium canicula are paired bodies in con- 

 tact along the median line. They are situated on the dorsal wall 

 of the abdominal cavity, and extend from close to the diaphragm 

 to a point a short way behind the anus. Externally, each appears 

 as a single gland, but by the arrangement of its ducts may be 

 divided into two distinct parts, an anterior and a posterior. 

 The former v/ill be spoken of as the Wolffian body, and the 

 latter as the kidney, from their respective homology with the 

 glands so named in higher Vertebrates. The grounds for these 

 determinations have already been fully dealt with both by 

 Semper'* and by myself. 



Externally both the Wolffian body and the kidney are more 

 or less clearly divided into segments, and though the breadth of 

 both glands as viewed from the ventral surface is fairly uni- 

 form, yet the hinder part of the kidney is very much thicker 

 and bulkier than the anterior part and than the whole of 

 the Wolffian body. In both sexes the Wolffian body is rather 

 longer than the kidney proper. Thus in a male example, 

 83 centimetres long, the two glands together measured 8J cen- 

 timetres and the kidney proper only 8^. In the male the 



1 Sitznnpsherichte d. Natnrfor. Ges. Leipzig, 1875. No. 2. 



2 Preliniiuary account of the development of Elasmobranch Fishes, Quarterly 

 Journal of Microscopical Science, 1874. Origin and History of the Urinogenital 

 organs of Vertebrates, Journal of Anat. and Physiol. Vol. x. 



^ Arbeiten, Semper, Vol. iii. 



4 Though Professor Semper has come to the same conclusions as myself with 

 respect to these homologies, yet he calls the Wolffian body Leydig's glaud after 

 its distinguished discoverer and its duct Leydig's duct. 



