40 
Bilharziasis 
probably assist the cercaria to cling to any stationary object, and in this way 
to gain entrance through the skin of its host. Lutz (1917) has noted on the 
head of the cercariae a ring of six or more small points, like the crown of a 
trephine, which may be considered to be a boring organ. This feature is not 
noted by Leiper, but the Japanese authors observed it in S. japonicum 
without attaching any importance to it. The oral sucker has a posterior 
prolongation (pharyngeal pouch), into which the ducts of the poison or salivary- 
mucin glands open. 
The ventral sucker or acetabulum is circular in outline and lies in the 
posterior fifth of the body, and when the cercaria is at rest the opening of this 
sucker is tri-radiate in shape. Lying immediately in front of the ventral 
sucker there is a small round brown pigmented simple gland of a granular 
consistency from which a small duct runs forward into the mouth. This can 
only be made out in fresh, but not in stained, specimens. 
On each side of this lie the “ poison cells” or salivary glands, each of 
which contains a well-marked nucleus, and from these individually a duct 
can be distinguished passing forward into the mouth. The number of these 
salivary-mucin glands varies in the two species, as pointed out by Faust, and 
which we have been able to confirm from our specimens. In S. mansoni cercaria 
(PL III, fig. 3) there are six pairs of glands altogether, of which two are large 
and clear with large nuclei and four are small and granular with correspondingly 
smaller nuclei. In S. haematobium cercaria (PI. Ill, fig. 4) there are three pairs 
of large clear cells with acidophil protoplasm and clear cut nuclei. In front of 
the salivary glands the primitive nerve ganglion divides into two branches; it 
would appear that this structure has been mistaken for the oesophagus. 
Immediately behind the ventral sucker there is a collection of densely 
packed nuclei, representing, probably, a primitive genital centre, and laterally 
placed to these are two oval excretory flame cells. The junction of the body 
and the tail is delimited by a membrane of oval shape and delicate con¬ 
sistency. The diameter of the tail diminishes towards the fork. Each arm of 
this fork tapers towards its termination and ends in a definite spike. The 
integument of the body as well as of the tail is covered with minute spines 
which can only be made out in the more mature cercariae, as has been described 
by Leiper for S. japonicum cercaria. 
The Excretory System. 
The excretory, or protonephridial system of these schistosome cercariae 
appears to be identical and has been described by Cort. It consists of six pairs 
of flame cells arranged along the margins of the body; from these cells capillary 
canals arise which join collecting tubules of a greater calibre running both in 
an anterior and a posterior direction. 
The excretory bladder consists of symmetrical convoluted tubes which 
project in a V-shaped manner just in front of the acetabulum (or posterior 
sucker), thence they run backwards and fuse at the junction of the tail to form 
