MAMMALIAN CESTODES. 9) 
character, which occasionally end below and in contact with 
the cuticle covering the body externally. I have not, however, 
observed any actual pores on to the exterior. I have also found 
the principal longitudinal vessel, which is the ventral vessel, as I 
judge, of the completely developed sexless worm. I believe this 
to be the case, since a transverse vessel arising from it was 
occasionally (see text-fig. 5) quite plainly to be recognised. 
I could not, however, find any continuous dorsal vessel lying 
to the inside of this, such as is very obvious in the later stage of 
the plerocercoid to be described immediately. 
Text-figure 5. 
Part of a transverse section of the same individual. 
B. Bladder-cavity. d. Water-vascular tubes. ¢.v. Transverse water-vascular 
tube. v.v. Ventral vessel. 
The larger specimen, which was examined by means of longi- 
tudinal sections, showed no great differences of structure from 
the smaller individual. The same four systems of cavities were 
distinguishable and presented the same characters. The spaces C, 
as shown in the accompanying text-figure (text-fig. 6), are in 
form roughly spherical and hardly at all elongate. They seem 
to be, on the whole, actually smaller than in the younger stage, 
which argues commencing disappearance, or rather reduction ; for, 
as will be seen later, these various spaces are quite recognisable 
in the completely developed and budding asexual worm. The 
bladder-cavity (B) seemed to me to be rather larger in proportion 
as well as actually than it is inthe younger plerocercoid ; and one 
would of course have expected the contrary. It is, however, not 
