
JOHNSTON AND BECKWITH—LARVAL TREMATODES 579 
contracted. The averages of measurements of six preserved metacerearia, given 
in niera, with the range in brackets, are as follows: length of body, 377 (819-410) ; 
breadth of body at widest part, 221 (205-237); length of anterior organ, 36 
(30-37) ; breadth of anterior organ, 34 (80-36) ; length of pharynx, 29 (28-30) ; 
breadth of pharynx, 25 (23-27) ; length of holdfast, 79 (63-95) ; breadth of hold- 
fast( 81 (66-90). The ventral sucker was not measured as if was very indistinet 
in most specimens, The six specimens measured were taken from a tadpole 
infected ten mouths previously. 
When the diplostomulum is uncompressed (fig. 16), it may be seen that the 
body is composed of two portions, a large leat-like anterior part, and a small 
posterior region, The anterior part is slightly concave ventrally and is furnished 
with a well-developed boldfast, beset ventrally with minnte spines (fig. 17). 
The posterior part contains the bladder and genital primordinm. 
The anterior part has wrown considerably more than has the acetabulum, 
which is situated immediately in front of the holdfast organ, The pharynx is stout 
and muscular, leading to a short oesophagus, followed by a pair of long slender 
caeea, extending to the posterior part of the body; the buleing ends, which 
characterized the cereavial stave, have not persisted, 
The bladder is composed of two lone horn-like branches, and has a single 
excretory pore on its posterior border. Prom each branch of the bladder a a stout 
collecting duct passes forwards on each side. Just in front of the level of the 
ventral sucker each duct receives a short colleeting tuhe into which open, firstly, 
a posterior tubule, passing back to the level of the bladder and receiving numerous 
lateral capillaries; and secondly. an anterior tubule also draining numbers of 
capillary tubes; this anterior tubule passes forwards to the level of the pharynx 
Where it bends mesiad and fuses with its fellow from the opposite side. From 
the point of fusion a central vessel passes posteriad, receiving many side-branches, 
Tu front of the ventral sucker if is joined by a commissure which passes from the 
branching end of one main colleeting duet to the other, The ecentral vessel 
continues posteriad to the region of the holdfast, where it ends in branches, 
The flame-cells have increased considerably iu number; a complete study 
was impracticable but the position of a nuniber is indicated on the diagram. 
Numerous refringent exeretory graniles ave present throughout the body, con- 
neeted with the newly developed capillary channels of the excretory system. 
RELATIONSHIPS. 
C. ameriannae is a Strigeid Jarva of the longifureate, pharyngeal, distome 
type. Since if possesses no excretory commissnre, il is at once distinguished from 
the Apharyngostrigea, Apaleman, aud Catylurus eereariae; the ouly notable point 
