40 



s. riOTO. 



sucker, on the ventral .side, where the l)n sèment membrane is some- 

 M'hnf indistinct ; l)nt they prohahly open also on the whole ventral 

 surface, altliongh I can not make a ]wsiH\'e statement to that effect 

 (PI. XX, fi<r. 10). In EpihtJrJla, on the other hand, the o'lands open 

 on tlie whole ventnd surface of tlie anterior sucker. Here, however, 

 it should he remarked that in most cases \ have not been ahle to 

 folloAv the ricck of the "'land-cells tlirovfjh the investing membrane of 

 the body to the external surface, l)ut only vp to the l)asement mem- 

 bi-ane. In T. ovale, on the other hand, the opening of the glands are 

 distinctly seen at the top of most of the conical papillae already men- 

 tioned. This lead>^ me to suppose that the ducts of the glands 

 tlu-ough the in\'esting membrane is usually entirely collapsed, Ijeing 

 open only during the actual passage of the secretion. It also leads 

 me to suspect whether l>randes'^ has not mistaken these glands for 

 his " subcuticular glands." 



In two species of Tristomvin, vi:. T. ^inuatmn arid T. hiparasiticinu, 

 there is, as before mentioned, a series of groups of peculiar unicellular 

 glands opening at intervals along the lateral margin of the body. 

 The series begins near the [interior end of the bodv, a.nd terminates 

 quite near the posterior sucker (PL XX, fig. 1 ; PI. XXV. fig. 5). In 

 T. siimatiim, I have counted as nrany as fifty-eight on one side of the 

 body, Avhile in T. liiparasilieum tliere were about sixty-two. I have 

 studied tlie histologv of these glands mairdy in the former species, so 

 that the following statements refer mainly to it alone ; but the es- 

 sential features are the same in l)oth species, the difference lying ordy 

 in insignificant details. 



The cells tliat constitute these glands are of various sizes, but are 

 more or less polyhedral in form, owing to mutual jrœssuiv. Each cell 

 has a distinct wall, and in the specimens I have exa.mined. the greater 



1). Brandes — /. r. 



