ON THE HEAD KIDNEY OF BDELLOSTOMA. 171 



On the Head Kidney of Bdellostoma, with a 

 Suggestion as to the Origin of the Supra- 

 renal Bodies. 



JBy 



liV. F. », ^VeldoBB, B.4., 



Scholar of St. John's College, Cambridge ; Demo-istrator of Comparative 



Anatomy in the University. 



With Plate XV. 



The structure of the greater part of the kidney of Bdello- 

 stoma and the Myxinoids generally lias been known since the 

 time of Johannes Miiller. It consists of a simple segmental 

 duct on each side, which represents both the "Wolffian and 

 Miillerian ducts of the higher Vertebrates, giving off in its 

 course a series of short tubules, each of which ends in a large 

 glomerulus. These tubules are segmentally arranged, a single 

 pair being present in every segment of the body in the anterior 

 three fourths of the region lying between the anus and the 

 hinder border of the pericardium. The relations of this system 

 of simple segmental tubules, opening into a segmental duct, 

 were described with perfect accuracy by Johannes Miiller ; ^ 

 and no important additions have since been made to the 

 account which he gave. 



The whole system obviously represents the Wolffian body of 

 the higher Vertebratea before the splitting of the segmental 

 duct into Wolffian and Miillerian ducts. 



In front of the kidney proper, however, there is on each 



1 ' Vergleichende Anatomie d. Myxinoiden,' Berlin, 1836—1845; 



