
JOHNSTON AND BECKWITH—LARVAL TREMATODES 577 
is striated transversely by wriukles, but these disappear when the body is 
extended, as in fig. 123. 
In front of the mouth are about thirteen fine spines, arranged alternately in 
two vows (fig. 12), There is a small circumoral spineless area, followed by a 
wide collar of 9-10 rows of spines, covering the anterior organ, Behind this the 
body is entirely covered with spines, arranged in rows over the anterior half of 
the body, and irregularly seattered more posteriorly. The ventral sueker ig beset 
with about seventy long slender spines arranged in two concentric rings. There 
is a single row of fine spines along each side of the fureae, 
The mouth opening (fig. 13) may be pushed forward or withdrawn deep into 
ihe anterior ovgan. Behind the latter is a short prepharynx followed by a stout 
museular pharynx, which is succeeded hy a narrow oesophagus, The latter 
bifurcates to form the two very long intestinal caeea. These are more than half 
as long as the whole body ; the longer anterior portion is narrow, but in the region 
of the ventral sucker they widen suddenly mto two pouches which extend back 
to the anterior border of the bladder, he wide part of the caeca stains faintly 
with intra-vitam neutral red, 
Immediately in front of the rather small ventral sucker, and ventral to the 
caeca, lie four large prominent penetration gland-cells, the cytoplasm of whieh 
stains with neutral red used intra-vitam. The highly characteristic arrangement 
of these is showu in fig. 18, The ducts of the four cells travel forwards, a pair on 
either side, and enter the anterior organ, the point of entry being marked by a 
constriction in their diameter. The duets open beside the mouth. 
Dorsal to the oesophagus, belind the pharyix, lies a transverse band of 
hervyous tissue. The genital primordium consists of a small, more or less triangular 
mass of cells, situated between the ends of the caeca and the bladder. 
The longifureate tail is very large relative to the body (fig. 14) ; both tail-stem 
and fureae are longer than the body, The tail-stem is very museular ; it contains 
no caudal bodies. 
The bladder is broad and slightly lobed ati cach lateral extremity. Each 
lobe receives a main collecting duct which passes forward, without coiling, to the 
level of the anterior border of the ventral sucker, where it receives two secondary 
tubules, an anterior, draining two pairs of flame-cells (fig. 12), and a posterior, 
draining a single flanie-cell and one pair in the body, and a further pair, well 



Vig. 12-18, Cercaria ameriannae, 12, spination and excretory system of body; 13, glandular, 
nervous, digestive and reproductive organs; 14. general proportions of cercaria, and excretory 
system of twil; 15. part of a sporocyst; 16. metsecerearia, uncompressed; 17, anatomy of 
metacercaria; 18. section through dorsal body wall of tadpolo showing metacereariae in situ 
in the notochord. Outlines of all figures were drawn with a camera lucida. 
dy = developing vertebra of tadpole; m = metacercaria; n = uotochord; ns = notochordal 
sheath, 
