TREMATODES OF AUSTRALIAN BIRDS. 237 



in the male. It measures 0*035 mm. in diameter. The 

 oesophagus is 0*2 mm. long, and divides into two intestinal 

 limbs just in front of the ventral sucker. The paired limbs 

 are very narrow and even, without diverticula, running 

 straight through the anterior part of the body. At the 

 junction of the anterior and posterior regions they fuse to 

 form a single much wider tube which runs straight back- 

 wards as a single tube to the posterior end, lying in the 

 middle of the body, surrounded on all sides by the yolk 

 glands. 



The ovary, measured in a straight line from its anterior 

 to its posterior end is 0*388 mm. long, but, as it is thrown 

 into a number of curves or waves along its whole course 

 its real length is much greater than this. The oviduct runs 

 forwards, placed nearly in the middle of the body; towards 

 its anterior end it widens into a uterus in which was found 

 in each case a single egg, 0*032 x 0*026 mm. in size. The 

 female genital opening lies immediately behind and to one 

 side of the ventral sucker. The yolk glands occupy the 

 whole field of the posterior part of the body up to the 

 extreme posterior end and extending forwards for a length 

 of 1*85 mm. 



This form shows, perhaps, closer affinities with Ornitho- 

 bilharzia^ than with the other genera of this family. The 

 members of that genus are found parasitic in European 

 species of Larus. In the males of the two genera the 

 external form, with the suckers is much the same: the 

 configuration of the intestine is very similar. The position 

 and arrangement of the testes are also fairly comparable 

 though the follicles are much less numerous and less exten- 

 sively distributed in Austrobilharzia. The position of the 

 genital pore is practically the same. In the females the 

 shape is somewhat similar as is also the arrangement of 

 the ovary and the yolk glands, though the anterior thread- 

 like part of the body is much longer in the Australian form,, 

 and the posterior broad part relatively shorter and conse- 



