1918.] T. Southwell & B. PrashAd : Pamdtes of Hilui. 85 



kinds of mviscles can be distinguished as forming the structures in ques- 

 tion. The posterior extremity of the worm is rounded. No opening 

 whatsoever is to be seen at this extremity. The outer cuticle is some- 

 what thickened. 



(3) Internal structure of the worm. — On examining the worm with the 

 high power it is seen to consist of a homogeneous substance in which no 

 differentiation into separate organs is to be observed. In fact, the 

 structure is of a most primitive character. All that can be distinguished 

 besides the egg-cells (E) and the coloured corpuscles, in both living 

 and stained specimens and in sections, is a tube, slightly coiled, which 

 runs round the worm, close to, and parallel with, the margin of the 

 leaf-shaped worm. Anteriorly, near the suckers, the two ends curve 

 inwards for a short distance towards the centre of the worm. This is 

 the excretory tube (E.t.), and from it are given off a large number of 

 minute tubules which end in typical flame cells. The flame can, with 

 an oil-immersion lens, be seen moving in these cells, in the livins 

 worm. The whole of the homogeneous substance referred to above 

 is filled up with enormous numbers of minute egg-cells. Besides the 

 eggs, morulae [(E (i)] and other higher stages in the development of 

 the young were also present in the intima. 



The orange-red coloured corpuscles (P. C.) are arranged in two 

 triangular patches, one on each side, immediately behind the suckers. 

 Each of these patches is formed of a large number of nearly rounded 

 corpuscles measuring 23-25 /x in diameter. We are unable to say 

 anything regarding the function of these corpuscles. When the worms 

 die, or are preserved, the pigment disappears. 



(4) Egg-cells. — The egg-cells (plate v, fig. 5) are elliptical, measuring 

 17 i^L by 12 \.L. The structures of the egg-cells is the same as that of a 

 typical ovum with little yolk, and they probably originate in the same 

 way as the parthenogenetic egg-cells in the sporocysts (and other larval 

 stages) of the Trematodes. Some of these egg-cells were seen to be in 

 different stages of development (plate v, fig. 6). They develop in the 

 body of the parent to form young worms identical in structure and 

 appearance with the parent. These will be fully described later on. 

 Under ordinary circumstances the anterior extremity, or rostellum, of 

 the adult worm shows no opening, but, when the development of the 

 parthenogenetic young worms is complete, it is seen that the young 

 worms have gradually worked their way to the anterior extremity of 

 the adult. They now escape through a temporary aperture which is 

 formed in the middle of the rostellum, anteriorly. In plate v, fig. 7 

 one such young worm is shown in the act of escaping. We were fortu- 

 nate in being able to observe two such cases, on different occasions, 

 in living animals under microscopic observation. After the parent form 

 has produced numbers of such young, the cyst breaks up and the young 

 escape into the mesentery of the host. The parent form now dies and 

 many empty cysts can always be seen in the mesentery of the host. 



(5) The young worms (plate v, fig. 8). — These vary in size from -3 mm. 

 to -35 mm. in length by -1 to -12 mm. in breadth. They, like the adult 

 worm, possess four suckers, a rostellum, imperfectly developed excretory 

 tube, and a few eggs, but are devoid of pigment. 



