PARORCHIS ACANTHUS, A NEW TREMATODE. 351 



nearer the middle line and more dorsal than the other. They 

 unite in a fairly small^ pear-shaped vesicula seminalis. This 

 is a simple structure, not included in the cirrus pouch, and 

 lying dorsal to the posterior half of the ventral sucker, 

 behind which it extends a short distance. It is near the 

 middle line of the body. The ductus ejaculatorius runs 

 dorsal to the ventral sucker; its terminal third is surrounded 

 by numerous prostatic glands. The penis, in its retracted 

 state, is represented by a short dilated sinus, the wall of 

 which is beset with numerous comparatively large spines. 

 The penis and prostate are enclosed in a thin membrane 

 forming the cirrus pouch. The genital aperture is situated 

 a short distance in front of the ventral sucker on a con- 

 spicuous oval papilla in the middle line of the body. 



The uterus has its beginning in the triangular area bounded 

 by the ovary and testes. After executing several windings 

 between these organs it proceeds to form convolutions run- 

 ning transversely from one side of the body to the other. 

 These convolutions extend some distance to the outer side of 

 the intestinal diverticula. They overlap the testes to a 

 slight extent, but do not pass behind them. Anteriorly they 

 are bounded by the ventral sucker. The vagina is well 

 developed, situated to the left of the ductus ejaculatorius 

 and dorsal to the ventral sucker. It opens on the left of the 

 male duct at the genital aperture. 



The ova are large and numerous, arranged in single file in 

 the uterus. They are elliptical in shape, and. the shell is of 

 alight yellow colour. Near the ovary the ova are darker, 

 and present the appearance of being in the process of seg- 

 mentation. They measure "081 — *095 mm. by "040 — '044 

 mm. Development takes place rapidly, however, so that 

 towards the middle of the uterus the almost fully formed 

 larva can be observed within the egg-capsule. The latter 

 has by this time increased in size to about '106 — '113 mm. 

 by '066 — '062 mm. Shortly after the extrusion of the ova, 

 which process I observed on one occasion,^ the capsule is 



' The previously-noted occurrence of ova in the ventral sucker was, I 



VOL. 51, PAET 2. NEW SERIES. 26 



