THE STRUCTURE AND FUNCTION OF THE ADULT 
HEAD KIDNEY OF BDELLOSTOMA STOUTI 
GEORGE C. PRICE 
Professor of Zoology, Leland Stanford Jr. University 
FOUR FIGURES 
At the anterior end of the kidneys of the myxinoids, in the peri- 
cardial cavity, is a pair of small bodies, which have been known 
for some years as the head kidneys or pronephroi. They were 
first observed by A. Retzius ('26) in Myxi le glutinosa, and were 
interprete j by him with some hesitation as the functional kidneys. 
Johannes ^Miiller ('45), w^ho was che first to give an accurate 
description of tne functional kidneys or mesonephroi, looked upon 
the kidneys of Retzius as suprarenal bodies. He worked on both 
Myxine glutinosa and Bdellostoma fos:eri 
Thirty years later Wil helm Mliller ('75), working on Myxine, 
described these organs more fully and more accuracel} than had 
been done by either of his predecessors, and came to tne con- 
clusion tnat they represented head kidneys or pronephroi. This 
interpretation has been generally accepted, and these organs nave 
have been homologized with organs of the same name in the larvae 
of amphibia and bony fishes. 
Since the appearance of Wilhelm ^Miiller's article the head kid- 
nev of Myxine has been made the subject of investigation by 
Kirkaldy C94), Semon ('96), Spengel ('97), and Maas ('97); 
while Weldon ('84) has described it for the gen is Bdellostoma, 
his work having been done on Bdellostoma fosteri, from the Cape 
of Good Hope. All these wwkers, with the exception of Maas, 
have labored under the disadvantage of having only adults at 
their disposal. The latter was particularly fortunate in obtain- 
ing three young specimens, the smallest only 8.5 cm. in length, 
