STUDIES OX THE ECTOPARASITIC TKEMA.TODES OF JAP AX. 115 



change, perhaps better fitting it to bear the abrasion to which it is 

 necessarily exposed during the formation of the egg-shell. 



Uterus — With this name I designate that portion of the female 

 eflfei'ent duct which is continued forwards from the ootyp and opens 

 to the exterior or into the genital atrium when such is present. In 

 Monocotyle it is, as already mentioned, wholly wanting, the ootyp 

 opening in this genus directly into the genital atrium. In Calicotyle 

 it is very short and is lined by the continuation of the epithelium of 

 the ootyp (PI. XIX, fig. 7) ; the cell-boundaries, however, can not be 

 observed satisfactorily. In Epibdella too the uterus is exceedingly short; 

 in fact it may be said to be wanting in E. Ishikawae. On the other 

 hand, in Axinc. ilicrocotyle, Hexacotyle, Octocotijle, and Diclidophwa the 

 uterus is very long, and its wall consists of a membrane which is in 

 most cases very thin, but sometimes very thick and refringent, as in 

 Microcotyle reticulata and Axine hcteroceixa (PI. \, fig. 5 ; PI. \ II, 

 fig. 1). In Octocotyle, Hexacotyle, Onchocotyle, and in all the species of Mi- 

 crocotyle except J/, sciaeme (PL VI, fig. 2), the inner surface of the uterine 

 wall is covered with cilia ; but in all the other species treated of in this 

 paper it is entirely naked (PI. V, figs. 1, 2, 3, 4, & 5 ; PI. YI, fig. 1 ; 

 PI. IX, fig. 12 ; PL XIV, fig. 3). In Axinc heterocerac and Dielidophora 

 nessilis the uterus is provided with a double layer of muscular fibres 

 consistinj? of the inner longitudinal and the outer circular fibres 

 (PL VII, fig. 1 ; PL XI, fig. 4). In Hexacotyle, on the other hand, 

 only the circular fibres are present. 



The uterine wall of Onchocotyle presents some peculiar aspects and 

 deserves a separate description. Close to the ootyp the wall of the 

 uterus presents an aspect closely similar to that of the ootj'p (PL XVI, 

 fig. 5) ; only the pilasters are lower and spindle-shaped in cross- 

 section, and some of them are seen to contain nuclei, which are mostly 

 oval and contain each a single nucleolus. Those that do not contain 



