X18 a. GOTO. 



OctocotijU, Diclidopliora, Onchocotyle, Moiiocotijle, and Galicotijle the 

 front attenuated portion of the body is entirely free from the vitel- 

 larium; the hinder caudal portion is also mostly free from it ; but to 

 many species this statement lioes not apply. In Diclidopliara tetrocloni)i 

 which has a very elongated body, the vitellarium is wholly absent from 

 the whole slender posterior portion. Ih many species of Tristomum 

 the vitellarium occupies not only the whole lateral portions of the body 

 but extends also into the median portion (T. ovale, T. Nozawae). In 

 Microcotyle, Octocotyle, Dididoplbora, Monocotijle, Galicotijle, Ejnbdella, 

 and in most species of Tristomum the vitellarium is present on the 

 dorsal and ventral sides of the body alike; but in Axiiic the ventral 

 side is mostly free from it (PL VII. fig. 1), and in Trist. ocale the 

 dorsal side of the median portion of the body is entirely occupied by 

 the vitellarium, which thus leaves only the ventral side for the testes 

 (PI. XXIII, fig. 7). In T. Xozawac too the vitellarium occupies in 

 the median portion of the body a position nearer the dorsum than the 

 testes; but in this species the vitelline lobes are more sparsely distributed 

 in this region. 



The vitellarium consists of numerous lobes, which are in most 

 species moi'e or less rounded, but are tubular in Galicotijle, so that in 

 this germs the vitellarium consists of a system of tubes filled with yolk- 

 cells. In Monocotijle, Onclwcotijle, Tristomum, Octocotyle, and in most 

 species of Microcotyle and DiclidopUora tliese lobes are very closely ag- 

 gregated, and leave only a very thin layer of mesenchyma between 

 them, so that they are very difficult to distinguish from each other in 

 sections (PL IX, fig. 7; PI. XI, fig. 3; PL XA^III, fig. 5); but in all 

 the other species the lobes are separated from each other by a more or 

 less thick layer of the intervening mesenchyma. For instance, in 

 Hexacotylc each lobe is surrounded on all sides by the mesenchyma, 

 which thus completely separates it from its neighbours (PL XI, fig. S; 



