STUDIES ON. THE DIGENETIC TREMATODES. 417 
' the papille in Dist. laureatum. On the strength of the 
foregoing alone I should be inclined to exclude Dist. 
laureatum from the genus Crepidostomum, for it is 
obvious that there is a wide interval of development between 
a condition of six and a corresponding condition of five 
papille, even although one or more of the latter is in the 
process of division. Further differences of generic impor- 
tance are, however, not difficult to seek. The first of these 
is to be found in the position of the genital aperture. In 
Braun’s figure it appears midway between the ventral sucker 
and the pharynx, and he describes it as close in front of the 
anterior border of the sucker. It is therefore considerably 
further back than in Dist. laureatum.! It appears single in 
Braun’s figure. ‘The cirrus-pouch is of great length, extend- 
ing beyond the ventral sucker by nearly half the diameter of 
the latter. In Dist. laureatum it barely reaches the centre 
of the sucker. Braun does not offer any details of the 
internal structure of the pouch. A noticeable feature in 
Crepidostomum metcecus is the enormous size of the 
testes, each being much larger than the ventral sucker, and 
their approximation to the posterior end of the body. This 
cannot be regarded as of very great importance. Of greater 
moment is the position of the ovary and the condition of the 
uterus. In Crepid. metccus the ovary hes not far in 
front of the anterior testis, on the right side of the body and 
separated from the ventral sucker by the cirrus-pouch. 
Braun makes no mention of amphitypy, although he had 
numerous specimens. The uterus is practically minimal in 
length and contains not more than two or three ova, which 
are much smaller (‘055 mm.) and broader than those of D. 
laureatum. Other features of difference are the nearly 
equal suckers, the somewhat small, round ventral sucker, 
and the absence of pre-pharynx and cesophagus in Crepido- 
‘ IT may be here accused of inconsistency in admitting the correctness 
of Braun’s observation while doubting that of Olsson ; but the justifica- 
tion lies inthe fact that many errors have been found throughout Olsson’s 
work, whereas Braun’s observations are, as a rule, beyond dispute. 
