DURING HIS SOJOURN IN THE WESTERN PACIFIC. 549 



ripe these grooves disappear to a great extent. The width of the ripe proglottides is 

 about 1 mm. and in outline they are nearly square. 



The reproductive opening is on one side of the body only and very irregularly 

 arranged, as is shown in Fig. 17 a, Plate LV. In many cases the older proglottides, 

 which are little more than thin sacs of ova, retain the penis in an extended condition 

 (Fig. 19, Plate LV.). 



The whole body is covered by an unusually thick cuticle which is well shown in 

 Figs. 18 and 20, Plate LV. The tissue within the cuticle is rather liable to contain 

 lacunae or splits between the cells, and this is especially the case where a prominence 

 protrudes between two grooves. The most striking of the histological features is the 

 sheath of longitudinal muscles which separate the central part of the proglottis in 

 which the reproductive organs lie from the more superficial tissues. This layer consists 

 of numerous longitudinal bundles very definitely arranged in the manner indicated in 

 Fig. lb, Plate LV. They take up the pigment of certain staining fluids with great 

 avidity, and as the muscles .separating one proglottis from another do the same, a 

 very characteristic, deeply stained, ladder-like muscular system is seen in longitudinal 

 section. This is well shown in Fig. 21, Plate LV., which represents a longitudinal 

 vertical section through a P. varani near the anterior end of the animal. In the head 

 the longitudinal muscles diverge and break up into something not unlike a shaving- 

 brush. 



Both the ventral and dorsal longitudinal vessels are seen in section through the 

 middle of the body (Fig. 18, Plate LV.). Posteriorly they tend to become smaller, and 

 this is especially the case with what I take to be the dorsal canal. This lies not 

 above but just external to the larger ventral vessel and both are included with the 

 tissue circumscribed by the deeply staining longitudinal muscles. The ventral vessel is 

 very capacious and slightly wavy in outline in that part of the body which succeeds 

 the head, but when the reproductive organs are well developed it diminishes much in 

 size. The connection of the vessels of one side with those of the other in the head 

 is simple and not plexiform. 



The reproductive system takes up but a small part of the space of a proglottis, 

 that circumscribed by the above mentioned deeply stained muscles. This space relative 

 to the surrounding tissues however increases in size as we pass backward first to the 

 mature proglottides and then to those which contain the eggs in utero. The more 

 advanced of these is little but a thin walled sac of ova, the surrounding tissue being 

 to a very great extent absorbed (Fig. 20, Plate LV.). Longitudinal section through the 

 anterior half of the animal shows that the primordia of the generative organs do not 

 correspond in number or po.sition with the external annulations, they are in fact far 

 more numerous, but this difference is soon adjusted and by the time the generative 

 glands are functional each set corresponds accurately with the region between two 

 annulations. 



Unfortunately the details of the arrangement of the testes, ovary and accessory 

 glands could not be made out. As was mentioned above the genital pore is unilateral, 

 and its distribution, on one or the other side of the body, is highly irregular. The 

 penis is often found in a state of protrusion and this even in the most mature 



73—2 



