216 Henry Leste OsBorx, 
the epithelial origin of the cuticle by direct alteration of the sur- 
face cells. 
The bladders in life pulsate simultaneously and somewhat 
rhythmically. The number of seconds between pulsations in one 
instance was found to be: 35, 28, 29, 40, 35, 45, 20, 55. At the 
moment of contraction the pore opens, after which it is closed and 
pursed up by the sphincter muscle. The contraction is a quick 
systole followed by a slow diastole, as if the former were a muscular 
act while perhaps the latter is not. Pulsations were noted in 
Aspidogaster by Huxury (1878) who states that the entire collecting 
vessel contracts unlike Cotylaspis where only the bladder contracts. 
Wricut & Macazzum (1887) report that in Sphyranura the two 
bladders do not contract simultaneously, that the systole is slower 
than the diastole and that the contraction does not completely 
obliterate the cavity of the bladder. In watching the living animal 
I could see at the junction of the bladder and the collecting vessel 
a distinct valve which closed and opened in connection with the 
contractions of the bladder but I have not preserved any records 
of the appearance of the valve in the living state. Sections passing 
through this region (Fig. 22) do not show any well defined and 
distinct valvular structures, and it would seem as if certain of the 
lining epithelium cells must perform this function. 
The collecting vessel is quite different from that of Aspido- 
gaster in its position and in the way the recurrent vessels connect 
with it. In C. insignis the vessel runs directly from the bladder 
forwards, passing dorsally to the diaphragm, to a point beside the 
pharynx, and there suddenly bends upon itself without changing its 
diameter and runs directly backward again till it reaches the point 
where the first branching arises. There are considerable differences 
as to the collecting vessel among the related genera. In Aspido- 
gaster (STAFFORD, 1893, fig. 8) the vessel passes almost at once 
through the diaphragm and runs torward to the front end of the 
foot, then it turns back narrowing as it does so and runs up into 
the body and then turns forward to a point beside the pharynx 
then turns back as in Cotylaspis. It would seem to function more 
as a bladder than in Cotylaspis. In Stichocotyle too the collecting 
vessel while in its location it is much like Cotylaspis is a large 
capacious vessel with the function of a bladder. Im Macraspis 
(JAGERSKIOLD, 1899) the vessel appears to be much the same as in 
Cotylaspis. In Cotylogaster it would seem from NicKerson’s figure 
eo: 
