420 WILLIAM NICOLL. 
CREADIIN® and allied forms has previously been remarked on 
by more than one author, and there is certainly no other 
known group to which they seem so closely: connected. 
Bunodera and Patagium, nevertheless, diverge widely 
from the ALLOCREADIINE in several respects. On the other 
hand, were it not for the circum-oral papille, Stephano- 
phiala laureata might be regarded as an Allocread. 
From the point of view of the circum-oral collar, the genera 
Patagium and Rhytidodes Lss. show the most primitive 
condition of a simple swelling of the muscle-substance of the 
sucker with commencing differentiation. The next stage, 
considerably removed, is that of Crepidostomum in which 
papille have appeared, showing a tendency to further sub- 
division, and the most advanced stage is that of Stephano- 
phiala, Bunodera and Acrodactyla, in each of which 
the condition is very similar, although, as I have tried to 
show, they may not be the direct evolutionary products of 
forms such as Crepidostomum, but may have proceeded 
along independent lines, the intermediate members of which 
have been lost or are not yet known. A consideration of the 
internal anatomy leaves hardly a doubt of this, for Stephano- 
phiala and Bunodera differ very much, while the former 
approaches Crepidostomum and the latter Patagium. 
From a detailed examination of the internal structures it is 
evident that Stephanophiala closely resembles the ALLo- 
CREADIINZ® in its most essential features, viz. the position of the 
genital aperture, the structure of the cirrus-pouch and its 
contents, the position of the testes, the extent and situation 
of the uterus, and the condition, size and number of the ova. 
This appears to have been noticed by Pratt! who included 
Crepidostomum Brn. in a sub-family, Pstosrominm Pratt, 
comprising Allocreadium and several allied genera,” while 
a1) 
| «American Naturalist,’ xxxvi, p. 888. 
> Pratt is rather inconsistent, for on p. 896 he notes : ‘ Yolk-glands 
do not extend in front of acetabulum” as a feature of the sub-family 
PsILostoMIn~”, while just above he has—* Yolk-glands extend in front 
of acetabulum,” under which sub-division he puts Calycodes Les., 
