ADULT HEAD KIDNEY OF BDELLOSTOMA STOUTI 861 
In Myxine, there is a glomerulus connected with the head kidney, 
which is so much like the one in Bdellostoma stouti that it seems 
it must have arisen in the same way. We know from the work of 
Semon that in some cases pronephric tubules open into the cav- 
ity of the glomerulus and in some they do not, and also that the 
cavity may be connected with the duct of the functional kidney. 
Spengel likewise found tubules opening into this cavit}^, and in 
addition found the cavity communicating with the pericardial 
cavity. WeldoQ mentions a glomerulus at the posterior end of the 
- g 
C 0 
Fig. 4 Diagrammatic longitudinal section, cv. , cardinal vein ; v, venous divertic- 
ulum; sin., sinusoids; cZ, central duct with openings into the venous diverticulum; 
neph., nephrostomes ; gl., glomerulus; a., artery of the glomerulus; vg., vein of 
the glomerulus. The cavity in which the glomerulus lies opens directly into the 
pericardial cavity and is connected with the central duct by two tubules, one of 
which has two nephrostomes. 
head kidney of Bdellostoma fosteri, but says nothing about a 
connection with either the pericardial cavity or the central duct. 
In a diagrammatic figure he represents a rudimentary connection 
with the duct of the functional kidney, and this he calls an atro- 
phied portion of the segmental duct, although it is more likely 
an atrophied tubule. 
Lying in front of the glomerulus in Myxine, and connected with 
the inner ends of the tubules, is a mass of peculiar tissue, in which 
arteries from the aorta ramify. This was looked upon by both 
Kirkaldy and Semon as being a mass of glomeruli. Spengel, on 
The Journal of Expekimextal Zoology, Vol. 9, no. 4. 
