TREMATODES OF AUSTRALIAN BIRDS. 209 



posterior end than the middle of the field. The size of the 

 testes is considerable, but not so large comparatively as in 

 some other members of the genus, (Nicoll (39) , fig. 7, and 

 Dietz (13) , fig. 36). The anterior, 0*291 mm. broad and long 

 is rather smaller than the posterior 0*35 X 0*31 mm. 



The ovary lies shortly in front of the anterior testis, on 

 the right side of the middle line. It is nearly spherical in 

 form, 0*126 x 0*116 mm. in size. There is no receptaculum 

 seminis, but the terminal part of the uterus is filled up with 

 sperms, forming a receptaculum seminis uterinum. The 

 space between the ovary and the testis is mainly taken up 

 by the large gland of Mehlis. The uterus is little coiled 

 and fairly long. 



The yolk glands consist of very numerous small follicles 

 varying in shape from spherical to oval, and in diameter 

 from 0*027 to 0*021 x 0*018 mm. In the extent of their 

 field they differ from all the other members of this genus, for 

 anteriorly they do not extend beyond a level halfway 

 between the ovary and the ventral sucker. From this 

 point they extend back in two lateral fields to the posterior 

 testis, behind which they spread over to the middle line 

 and almost reach the posterior extremity. 



The eggs are large and showed little variation in size, 

 the average measurement of a large number measured 

 being 0*084 x 0*058 mm. 



The nearest relative of this worm, E. coaxatus, Dietz, is 

 also parasitic in a water bird, the crested grebe, Podiceps 

 cristatus. The two worms differ in a number of points. 

 The collar spines of E. coaxatus are distinctly longer than 

 those of E. tenuicollis. The relative size of the suckers 

 is quite different, being 1 : 5 in the latter and 1 : 2 in the 

 former. The shape of the testes is different and the cirrus 

 sac larger in the Australian form, but one of the most strik- 

 ing differences is in the stopping short of the yolk gland 



N— December 6, 1916. 



