E. C. Faust 
255 
A careful study of the flame-cells and connecting capillaries of C. crista- 
cantha shows that there are 12 sets of two on each side of the body, making 
24 for each side of the body or a total of 48 flame-cells for the larva. The picture 
of a dichotomous arrangement of flame-cells in the body of an echinostome is 
altogether unique, all previous records having indicated a trichotomous group¬ 
ing. On this assumption (Faust, 1919: 334) I have indicated two groups, one 
consisting of a single cluster of three (a group) and a second containing the a 
cluster and an additional cluster or series designated as p. Thus, in C. chiso- 
lenata only the a group is found, while in C. complexa the a group (3) and the 
P group (12) make up a total of 15 flame-cells. 
In G. cristacantha , however, although an analysis of very young larvae 
indicates an original a + ft condition, subsequent forking of each series behaves 
in such a way that (I) a trifurcation of each group occurs, (2) followed by an 
additional bifurcation. Thus the original a + p groups obtain here as in here¬ 
tofore described species and, primitively also, the 3-flame-cell cluster of each 
group, but, in addition, a later dichotomy has been superimposed on the 
original and fundamental pattern. Thus the system may be expressed as 
[(2 + 2 ) + (2 + 2 ) + (2 + 2 )] + [(2 + 2 ) + (2 + 2 ) + (2 + 2 )], 
for which the formula a n + P n holds. This, on expansion, becomes 
a 1 + a n + a m + « iv 4- a v + a yl + p [ + P n + p m + p iv + + 
Moreover, this same pattern has been impressed on the redia (a, p. Fig. 6), 
for here, too, there is a distinct anterior (a) group and a posterior (p) group for 
each side of the larva, the two joining to empty through a common excretory 
pore (ep). Furthermore, here, too, there is the identical pattern which was 
found to obtain for the cercaria, namely, for each group pairs of capillaries 
and flame-cells. 
The circumstance of this 2x3x2 pattern for each a and p group is not, 
therefore, a variable phenomenon, but rather a sub-group characteristic, the 
analysis of which adds materially to our conception of the lines of divergence 
in the group. 
Cercaria leptoderma nov. spec. 
(Plate XXI, Figs. 7-11.) 
This larva, for which the name Cercaria leptoderma is proposed, was found 
once out of a total of more than 2000 specimens of Viviparus quadratus (Bens.) 
examined from the Peking area. The parasites were taken from the liver gland 
of the host. 
The mature larva is extremely active and of sufficient size to be easily seen 
without the aid of the microscope. The body measures 0-35 mm. in length 
by 0*15 mm. in width, while the long, narrow median shank of the tail has a 
length of about 0-6 mm. and the furci measure about 0*15 mm. The furci are 
flat, sharp blades. The entire worm is aspinose except for a cap of sharp hooks 
set on the anterior end of the cercaria. 
17—2 
