TREMATODES OF AUSTRALIAN BIRDS. 191 



the intestinal limbs and divide each into two branches, 

 one of which runs forwards and inwards, the other back- 

 wards and inwards (fig. 1). 



In addition to these vessels, a number of minute vessels 

 arise from the vesicle at various points, and end in flame 

 cells. The flame cell (fig. la) has a rounded body with a 

 large nucleus and an elongated tuft of cilia. 



Nervous System. — The cerebral ganglia lie just behind 

 the pharynx, one on either side of the oesophagus. Large 

 nerve trunks pass off from them backwards and outwards 

 to the lateral border of the wings (fig. 1). 



Yd. Ex* 



Fig. 2. — Transverse section through the region of one of the testes, 

 showing the space by which the testis is surrounded, and the strands of 

 connective tissue by which it is held in place. Ex. v., excretory vesicle ; 

 Int., intestine; Sp., spaces round the testis; Si., strands crossing the 

 space ; V.d , vas deferens ; T.g., yolk-glands. 



Genitalia. — The genital opening lies in the depth of the 

 genital sinus, which is situated just in front of the junction 

 of the wide anterior and the narrow posterior parts of the 

 body. The ventral sucker, bounding the genital sinus in 

 front is placed 0*543 mm., behind the oral sucker. The 

 gonads lie in a straight line, one behind the other in the 

 posterior half of the body, the ovary in front and the testes 

 behind. The testes are large, oval, fairly solid bodies, 

 (fig. 1), the surfaces raised up into a few wide, low ridges, 

 but not deeply divided into lobes as in S. expansus. They 

 are approximately equal in size and lie with their long 



