426 Records oj the Indian Museum. [Vol. XVI, 



ous lashing of the tail. Under a cover slip it only makes feeble 

 ])rogress owing to the fact that its anterior end appears to be 

 not a true sucker but an organ devised for penetrating the host 

 tissues. The body is frequently bent from side to side and is cap- 

 able of a very great degree of extension and retraction. Further- 

 more, the anterior end forms a protrusible snout which is some- 

 times thrust out to form a round papilla and from time to time is 

 retracted within the anterior end of the animal, thus forming a 

 depression which at first sight might be thought to be the cavity 

 of an anterior sucker. The animal has a marked tendency to shed 

 its tail while under observation. 



Owing to the extreme degree of extension and retraction of the 

 animal it Is difficult to get the exact measurements in the live state. 

 So far as my observations go the measurements of the cercaria 

 are as follows : — 



When the body is extended it measures o*ig6 mm. in length 

 X 0*025 iT^in- ii^ breadth and when contracted o'ogo mm. x o'05o 

 mm. The tail seems to be capable of a certain degree of exten- 

 sion and varies in length in different specimens from 0'i86 too' 221 

 mm. The furcal rami are short and are capable of extension 

 and contraction, having in a contracted condition a wrinkled 

 appearance. They vary in length from 0*071 to 0-096 mm. The 

 body is comparatively transparent and in consequence it is very 

 easy to make out the details of the structure. The whole of its 

 surface is covered by minute spines which extend as far forward as 

 the limit where the body-wall joins the sides of the anterior 

 sucker-like structure. The tail is rather more sparsely covered 

 with spines that appear to be slightly hooked and are com- 

 paratively large and both furcal rami are armed with spines along 

 the margins. The anterior sucker-like structure is pyriform in 

 shape and measures 0'043 mm. by 0*032 mm. when the animal is 

 in the state of retraction but during the extension of the body this 

 pyriform mass becomes considerably longer and narrower. Behind 

 the point wnere the body-wall joins the anterior " sucker " the 

 wall of this latter organ is thick and is provided with a strong 

 layer of circular muscle-fibres. Internally the great bulk of the 

 organ is filled with a granular mass, the head gland, while laterally 

 and posteriorly are a number of small parenchymatous cells, also 

 granular in appearance : the ducts from the cephalic glands, of 

 which there are five on each side, enter this pyriform structure on 

 its ventro-lateral aspect and pass forwards to open at the tip of the 

 protrusible snout. Each duct is tipped at its orifice by a hollow 

 conical spine of which there are ten in all. The acetabulum is 

 small and is situated about |- the distance from the posterior end 

 of the body, its external opening is Y-shaped, the two limbs of 

 the Y pointing forwards and one limb backwards : it measures in 

 diameter 0"0i4 mm. Its external surface is covered with a number 

 of fine spines and it is capable of some degree of protrusion and 

 retraction but normally forms only a small projection on the ven- 

 tral aspect. 



