92 Records of the Indian Museum. [Vol. XIX, 



it is somewhat dilated and from this dilated portion a short canal 

 passes backwards to the excretory pore {cxp.), which is situated 

 at the extreme posterior end of tlie body. Anteriorly the 

 bladder becomes somewhat dilated and it terminates in two very 

 short and wide lateral diverticula. From each diverticulum a 

 short common collecting tube (cct.) can be traced forwards and 

 outwards to a point opposite the posterior margin of the aceta- 

 bulum, where it divides into anterior (act.) and posterior {pet.) 

 collecting tubes, rumiing forwards and backwards respectively in 

 the lateral region of the bod}'. Both anterior and posterior collect 

 ing tubes receive three accessory collecting tubes {acct.), each of 

 which is formed by the union of three capillary vessels originating 

 in three flame cells : of these capillary vessels two unite together to 

 form a single trunk and this is then joined by the capillary of the 

 third flame cell, thus showing what Cort (1919, p. 290) has termed 

 the "two-one" arrangement in the capillary groups. The excre- 

 tory system of this species is summarised in the formula 2 X 

 6x3, and in fig. 4 I have shown the distribution and arrangement 

 of the capillary groups and collecting tubes. A comparison of this 

 figure and those given by Cort of the excretory systems of Cercaria 

 polyadena {Ic, 1919 (a), p. 277) and Margeana californiensis 

 {I.e., 1919 (b), p. 293) shows that in all three the sj^stems are 

 identical. 



As almost the whole of my researches on this species, Meso- 

 coelium sociale Liihe, were confined to the study of living examples, 

 it was found to be impossible to work out the nervous system in 

 detail. On either side of the oesophagus lies a ganglionic mass 

 which is connected across the middle line with its fellow of the 

 opposite side by a short stout commissure running dorsally to the 

 alimentary canal : a pair of large ventral nerves can be traced 

 backwards on the ventral aspect, extending as far as the posteiior 

 ends of the intestinal caeca, and a smaller dorsal pair of nerves 

 can be made out on the upper aspect of the body ; while several 

 smaller nerves appear to pass forwards around the oral sucker 

 towards the anterior end of the body. 



Development. 



At the present time nothing is known regarding the larval 

 development of this species. Cort (1919 (b), p. 295) has put for- 

 ward the view that Margeana californiensis, which he places 

 in the subfamily Brachycoeliinae Ivooss, is developed from a 

 cercaria that in all probability will be found to belong to the 

 Polyadenous group of the Xiphidiocercariae. This sub-group of 

 cercariae was created by Cort (1914, p. 53) to accomxmodate certain 

 forms that possess quite distinctive characters dividing them off 

 from other of the Xiphidiocercaria groups. Omitting certain 

 entirely larval characters, the Polyadenous cercariae were shown 

 by him to possess the following anatomical features : — 



(i) Acetabulum smaller than the oral sucker. 



