Habits and structure of Cotylaspis insignis Leıpy. 215 
indistinct, owing to their small size and the thickness of the cuticle 
through which they must be seen. The bladders and collecting 
vessels can be studied in sections, but none of the rest of the 
system were seen in sections or in any kind of preserved material. 
The excretory pore is single and located on the summit of a 
low eminence near the hind end of the body (Fig. 7). The two 
bladders, which are entirely free from each other elsewhere, meet 
here and reach the terminal pore by a short tube. The bladders 
are ovai and decidedly larger than the collecting vessel beyond. 
These parts are not the same in the family at large. In Macraspis 
there is a short unpaired bladder (as in trematodes generally); in 
Aspidogaster the collecting vessels are slightly swollen near the tips, 
and after meeting diverge and open by two separate and distinct 
pores; in Cotylogaster occidentalis there are two separate very thin- 
walled bladders with a single median pore, which opens at the base 
of the dorsal cone (NickERson, 1899); in Stichocotyle the function of 
a bladder is assumed by the very large collecting vessels, which 
communicate with the exterior by means of two very narrow tubes 
which join and form a single short and very slender one. In all 
these cases the excretory opening is located posteriorly and dorsally. 
In ©. insignis the cuticle is directly continuous from the surface into 
the terminal tube (Fig. 21) and with that of the outer parts of the 
wall of the bladder. Distinct muscles exist among them fibres 
which circling around the pore act as a sphincter to close it. The 
wall of the bladders is supplied with a continuation of the longi- 
tudinal muscular coat of the collecting vessel, circular fibres were 
not seen. The parenchyma condenses around the bladder as around 
some other organs (e. g. the cirrus sack) its fibres and nuclei being 
much more numerous. The inner lining of the bladder is cuticular 
nearer the surface, this shading imperceptibly into a distinct 
nucleated epithelium as the collecting vessel is approached, through 
a transitional type. Fig. 22 is from a section passing through the 
length of the bladder and into the collecting vessel. Granular 
protoplasm and healthy nuclei are distinctly present. Near these 
healthy cells, there are masses of granular protoplasm containing 
dense deeply stained masses evidently the remains of nuclei which 
have degenerated. These I regard as being cells which precede 
the cuticle and similar to those from which it has been developed. 
The indication here as in case of the oesophagus is favorable to 
