6 DR. F. E. BEDDARD ON 
later, be termed the anterior end. But although there are facts 
which point to the view that this is the anterior end, there 
appears to be no difference in minute structure between the two 
ends of the worm. There is not even the rudimentary scolex 
marked chiefly by its pigmentation, which I referred to in 
my earlier description of the sexless form of this worm. The 
cavities which occupy so much of the inside of the body can be 
referred to four categories, and their differences are rendered 
clear in text-figure 2. The cavity lettered “A” is distinguished 
from the others by the structure of its walls. It is lined by a 
structureless layer (see text-fig. 3) which quite resembles the 
external cuticle of the worm. Round this cuticle are stalked 
Text-figure 4. 
Transverse section through the same larva as that represented in text-fig. 1, E, 
in a place where the cavities C only are to be seen. 
d. Water-vascular tubes. 
glandular cells which are quite like those of the subcuticular 
layer. These cells are very conspicuous, as is shown in the 
figure. The cavities are the expression in transverse section of 
tubes which are shortand do not branch so far as I could discover. 
The obvious similarity to the external layer of the body which 
they show led me to expect that an opening or openings on to 
the exterior would be found. I have not, however, obtained 
perfectly satisfactory evidence of such, and indeed have found no 
actual orifice at all. In the case of one of these tubes, which I 
