318 ON SOME TKEMATODE PARASITES OF AUSTRALIAN FROGS, 



found it only twice. The alimentary canal exhibits the well- 

 developed pre-pharynx characteristic of the group. The 

 spherical pharynx, with its front edge indented, has strong 

 muscular walls, and the oesophagus is equal in length to the 

 pharynx (Fig. 52). The photograph (51 ) shows the intestinal 

 limbs reachhig to the extreme posterior end of the body. The 

 Y-shaped excretory vesicle has a comparatively long stem, 

 which, like that of Astiotrema (Looss, 50), winds between the 

 testes, and divides into its two branches just behind the shell- 

 gland (Fig. 54). The cirrus-sac lies wholly in front of the 

 ventral sucker as in Opiathioylyphe : the seminal vesicle is 

 constricted in the middle like that of Dolichosaccm ; the copu- 

 latory organs are strongly developed. As regards the location 

 of the gonads, the ovary is generally on the right of the middle 

 line, while the left testis is anterior to the right ; but the 

 sexual amphitype is of frequent occurrence, 28 per cent, of 

 the individuals exhibiting this curious variation. Laurer's 

 canal is of extraordinary length. Its course is less tortuous 

 than in DoUchomccus, but it runs right down to near the pos- 

 terior end, opening on the dorsal surface quite near the blind 

 ends of the intestines (Fig. 53). The extension of the yolk- 

 glands is also peculiar. On the right side, they occupy the 

 space between the lateral body-wall and the intestinal limb, 

 stretching from just behind the intestinal fork back to the 

 level of the posterior testes, and do not anywhere extend in- 

 wards beyond the intestinal limb. On the left side, their 

 disposition in front of the testes is exactly the same as that 

 on the right, but they extend further back, and, stretching 

 inwards behind the testes, partly fill up the space lying be- 

 tween those organs and the posterior end of the body. This 

 distribution of the yolk-glands is a very constant character, 

 being exactly similar in every specimen, except that in the 

 sexual amphitype, of course, it is the follicles on the right- 

 hand side that extend beyond the testes. 



The coiling of the uterus is very rich and complex, so that, 

 although its calibre is only small, all the body-space between 



