364 
A. M. REESE 
bands separated by more transparent areas of about the same 
width. Because of their inclination, transverse sections rarely, 
if ever, show the entire circumference of the rings. 
In Rhinochimsera, as well as can be judged from Garman's 
figure ('04), the fibrous rings are not completely separated from 
each other by other tissue, and they break up into smaller branches 
much nearer the bottom of the canal than is the case in C. colliei. 
In the extreme tip of the tail the animal is so compressed lat- 
erally that the fibrous rings, in spite of their small size are prac- 
ticall}^ in contact with each other in the median plane (fig. 16). 
In other parts of the system the rings are surrounded by the more 
or less dense mass of fibrous tissue of the dermis. 
The shelf that has already been noticed, in connection with 
the canals of type 2, is seen, in cross section (fig. 14, g), to be due 
to a large group of glands, arranged, mainly around the periphery 
of the wide spaces in the canal. What the character and purpose 
of the secretion of these glands may be could not be determined. 
In some regions of the canal this secretion seemed to almost fill 
the lumen, while at other places it was practically wanting. 
The lining epithelium of the canals, which is especially modified 
at certain regions to form the sense organs, is directly continuous 
with the outer layers of the epidermis of the body integument. 
The sensory epithelium of the first type of canal will be described 
first. The epidermis of the body integument varies considerably 
in thickness, but where it turns inward to form the lining of the 
canal it becomes much thinner, usually with some suddenness. 
Owing to unsatisfactory fixation, as has been mentioned above, 
the minuter structures of the lining epithelium could not be deter- 
mined, especially in the parts of the canal nearer the opening. 
In these regions of the canal the epithelium lies close to the carti- 
laginous and fibrous rings, to which it is united by a thin layer 
of less dense fibrous tissue. This layer seems easily torn, for the 
epithelium is, in many cases, torn away from the surrounding 
rings. The epithelium here consists, as nearly as can be determined, 
of a few layers of small, irregular cells — a sort of transitional 
epithelium. As the bottom of the canal is approached this epithe- 
lium, especially in certain regions, to be noted shortly, suddenly 
