Habits and structure of Cotylaspis insignis Leıpy. 217 
ud 
(1902, fig. 15) that the collecting vessel and bladders are much as 
in Cotylaspis, the bladder being longer but equally distinct from the 
collecting vessel. Concretionary structures are reported from the 
collecting vessel in Aspidogaster and Stichocotyle, as well as in other 
trematodes (Prarr, 1898, Apoblema), none are found in C. insignis. 
The wall of vessel (Fig. 24) is composed of longitudinal muscle 
fibres, very few in number, no circular fibres, and a distinct lining 
of epithelium composed of somewhat flattened cells with abundant 
cytoplasm and nuclei. There are no ciliary organs in the collecting 
vessel, but they are readily seen (Fig. 27) in the recurrent vessel 
just around the turn from it. 
The vessel which continues the collecting vessel I have for 
convenience called the “recurrent vessel”. It runs backward to the 
level of the foot where it sub-divides to form an anterior and 
posterior branch. The recurrent vessel and its branches are furnished 
at frequent intervals with vibratile structures which produce a 
current running out toward the collecting vessel. In the living 
animal they are barely visible at first but as the animal becomes 
enfeebled and they move more slowly they appear (Fig. 28) like a 
rapidly revolving screw. The walls of these vessels are very thin. 
At intervals large nuclei are attached to it, and here in sections 
one sees clusters of long cilia, rendering it evident that the large 
solid looking vibratile objects of the living vessel are peculiar organs 
composed of clusters of very long cilia closely adhering and working 
in unison. These organs seem to be very much the same as those 
of Aspidogaster according to Starrorp, and I have found similar 
organs in the excretory vessels of Clinostomum. It is strange that 
in the case of such powerful ciliary organs the body of the cell in 
connection with the cilia should not be larger and contain a distinct 
ageregation of protoplasm, but I have not been able to find any 
evidence of a cell body at all commensurate with the ciliary organs 
in connection with them. They thus seem to be of quite a different 
structural type from the ciliary organs of the ctenophores though 
functionally somewhat comparable. 
I did not succeed in tracing all the branchings of the ultimate 
excretory vessels. There does not seem as in Aspidogaster to be 
any definite trichotomous plan. One of the ultimate branches is 
shown in Fig. 26 where a small vessel leads from the anterior branch 
of the recurrent vessel to the capillaries in connection with the 
flame cells. The final capillaries are not ciliated next the flame 
