Nos. IAND2.] COTYLASPIS INSIGNIS. 19 



opens, after which it is closed and presents a puckering appear- 

 ance, indicative of the action of the sphincter already noticed. The 

 contraction is a quick systole, followed by a slow diastole, at the 

 end of w^hich a second contraction follows and so on. Counts of 

 the seconds between a number of successive contractions were : 

 35, 28, 21, 29, 40, 35, 45, 20, 55 in one instance. Wright and 

 Macallum '87 found that in S phyranura the two bladders did not 

 contract simultaneously, and that there was no constant rate ; that 

 the systole was slower than the diastole and did not obliterate the 

 cavity of the bladder. 



The junction of the excretory bladder and the collecting vessel 

 are easily seen in life, and at this point I have clearly seen a valve 

 which opened and shut in correspondence with the pulsations of 

 the bladder. The collecting vessed runs in the central level of the 

 body, and when it reaches the diaphragm it passes dorsally to it, 

 and runs directly to the level of the pharynx (Fig. 3). This is 

 very unlike Aspidogaster, where " the anterior ends of these ves- 

 sels project far into the forward prolongation of the ' foot' (to 

 within o.io mm. of its anterior border) and suddenly narrow to 

 much smaller tubes which bend directly back along the collecting 

 vessels before rising to the neck region" (Stafford '96, p. 33), 

 and thus the vessel is beneath the diaphragm. In Stichocotyle the 

 collecting vessel, though similar in location, is structurally unlike 

 that of Cotylaspis, being very much enlarged and communicating 

 with the exterior by means of a very much narrowed passage; 

 instead of being smaller than the excretory bladder it is much 

 larger and assists its function. In Macraspis the collecting vessel 

 appears from Jagerskiold '99 to be much as it is in Cotylaspis. 

 The wall of the collecting vessel in Cotylaspis consists of a 

 distinct epithelium with nuclei at frequent intervals. The cells 

 are not flattened so as to leave the nuclei bulging, but contain 

 considerable cytoplasm ( Fig. 22 ) . In no case have I been able to 

 detect cilia or flagella in the collecting vessels, and I am convinced 

 that they are wanting, though they are readily seen, as in Fig. 25, 

 just at the point where the vessel passes into the recurrent vessel. 

 The lumen of the collecting vessel is distinct, and I have examined 

 it repeatedly for concretionary structures like those reported by 

 Stafford, Nickerson and Pratt for Aspidogaster, Stichocotyle and 



