856 
GEORGE C. PRICE 
The tubules are so numerous and so closely packed together 
that it was entirely out of the question to try to count them after 
sectioning. While an idea of the number in a small individual 
could be gained by first staining the entire organ and then counting 
the nephrostomes under a strong lens, this method could not be 
used with large individuals, in which the number ran into the 
thousands. But by first staining the entire organ, and then 
teasing into small pieces in glycerin, and counting under the com- 
pound microscope, a rough idea of the number of tubules in several 
individuals of different sizes was obtained. In this way 265 tu- 
bules were counted in a head kidney from an individual 29.2 cm. 
long, 791 in one from an individual 34.2 cm. long, 6084 in one 
from an individual 49.5 cm. long in which the head kidney was 
was unusually large, and 2300 in one from an individual 56.5 cm. 
long. In all cases the actual number must have been greater 
than the number counted, for it was not possible to get all the 
pieces so small that every tubule could be seen. In the case where 
265 tubules were counted at least 300 nephrostomes were seen 
before teasing. It will be noticed that the largest and presumably 
the oldest individual did not have half so many tubules as the 
one next smaller. Pernaps the first explanation that would sug- 
gest itself for this would be that it was due (o degeneration and 
the consequent disappearance of tubules. But this is not likely 
the case, for so far as possible in counting, every tubule was ob- 
served, and no indication of degeneration was noticed. Further, 
this is not so surprising when we take into consideration the great 
amount of variation in all parts of the organ. 
The average diameter of a number of tubules from three individ- 
uals of different sizes was 0.055 mm., and the average diameter 
in the largest individual was no greater than in the one under 
three inches long. As a rule there is but slight variation in the 
size of the tubules in an individual ; but in some instances, espe- 
cially in larger individuals, a portion of atub ulema}^ be so enlarged 
as to form a vesicle as much as four times the diameter of an ordi- 
nary tubule. These vesicles were absent in more than half the 
head kidneys examined. When present they varied in number 
from two to seven. As has been observed in other members of 
