
574 RECORDS OF THE S.A. MUSEUM 
The spination is sparse, mainly confined to the anterior part of the body, The 
pharyngeate alimentary canal ends in caeca which are short, faint and may be 
lobed. The penetration glands are eight in number, except in the doubtful 
C'. riponi; these glands are usually behind the ventral sucker. The variations 
in their arrangement constitute an important means of species identification. 
When arranged in order according to the disposition of their gland-ceells, the 
cercariae form a fairly definite series, from the cerearia of Apatemon gracilis, 
with glands in two horizontal rows, through @, psewloburti and C. burli, with 
glands more longitudinally disposed in elusters, to C. helvetien XXXL, C. pygo- 
cytophora and (. lessoni, in which the glands have become drawn out into two 
longitudinal rows (fig. 10). 
Perhaps another characteristic of the Apatemon cervariae is the presence 
of unpigmented eyespots, though they are not described in all. The tail is always 
longifurcate; the tail-stem, body and fureae are of much the same length in each 
cercaria. The flame-cell formula is 2/2 + (2-4.2-+ (1))]=14. The presence 
of only two flame-cells in the tail-stem, instead of four, as is usual in Cotylurus 
and Diplostome cercariae, and their position immediately behind the junction of 
hody aud tail is an invariable feature, Sewell (1922, 267) in discussing C. indica I, 
sole member of his Pahila group, considers that the presence of a single flaine-eell 
pair in the tail-stem is probably a group character rather than a specific difference, 
a view which this set of cercariae tends to support; but the feature also 
characterizes another group, Miller's Zlvge group of ocellate eereariae, whieh are 
not otherwise closely related, as well as various other cercariae, mentioned above, 
which are not closely allied to the Apatemon cereariae. This character is hence 
merely indicative and not diagnostic until considered with the other special 
features. Likewise, the position of the excretory pores of the tail, half-way along 
the furcae, is typical not only of the Apatemon cercariae, but also of many 
Cotylurus and Diplostomum cercariae. 
The early development of parts of the reserye excretory system is a further 
characteristic of the Apateman eereariae. This allies them to the Colylurus group, 
in contrast with the Diplostome cereariae, In the former, the commissure usually 
developed is that anterior to the ventral sucker; in the Apufemon group, four 
of the seven cereariae possess one commissure, posterior to the ventral sucker, 
while the other three (C_ helvetica NX NT, C, pyyocytophora and C, lessoni) display 
variability in the extent to which the commissures are developed. C. helvetica 
XXAT, the most precocious, has two fully developed cammissures; C. pygocyto- 
phora shows least development, with only an anterior commissure, incompletely 
developed; while in C. lessoni growth and fusion of the two commissures takes place 
toa variable extent in cercarial life, Precocious development of the reserve systent 
bas been observed in a number of cercariae, c.g. . sunguanensis Miller, in whieh 
