238 



S. J. JOHNSTON. 



quently the extent of the yolk glands much less; the ovary 

 is also shorter. While the female is shorter than the male 

 in Ornithobilharzia, it is longer in Austrobilharzia. While 

 spines are quite absent in the Australian form, except on 

 the ventral sucker of the male, in Ornithobilharzia the 

 gynecophoral canal of the male is thickly lined with small 

 pointed spines, and the female has the posterior flattened 

 part of its body armed with thick spines, which only cease 

 at the extreme posterior end. (42) In the latter, too, the 

 vesicula seminalis lies quite outside the rudimentary cirrus 

 sac and a prostate is absent, but in the former the cirrus 

 sac is well developed and completely encloses the seminal 

 vesicle, and contains well developed prostate cells lying in 

 its parenchyma (fig. 21). 



The structural relations between the five genera of this 

 family may be seen at a glance in the following table: — 





Bilharzia. 



Bilharziella. 



A ustro- 

 bilharzia. 



Ornitho- 

 bilharzia. 



Giganto- 

 bilharzia. 



Compara- 

 tive size of 

 male and 

 female 



female 

 longer than 

 male 



female 

 shorter than 

 male 



female 

 longer than 

 maLe 



female 

 shorter than 

 male 



female 

 shorter than 

 male 



Suckers 



present 



present or 

 absent 



two in male 

 one in female 



present 



absent 



Spines 



numerous in 

 both male 

 and female 



only on 

 suckers 



only on ven- 

 tral sucker 

 of male 



numerous in 

 both male 

 and female 



absent 



Genital 

 pore of 

 female 



immediately 

 behind the 

 ventral 

 sucker 



far behind 

 the ventral 

 sucker 



close behind 

 the ventral 

 sucker 



behind ven- 

 tral sucker 



near anter- 

 ior end 



1 Testes 



few 



numerous 



not numer- 

 ous, occupy 

 small field 



numerous 

 follicles 



very numer- 

 ous reaching 

 posterior 

 end 



poorly 



developed 



Cirrus sac 



absent 



well devel- 

 oped but not 

 enclosing 

 vesicula 

 seminalis 



well devel- 

 oped and 

 enclosing 

 vesicula 

 seminalis 



rudimentaFy 



Prostate 



absent 



present 



present 



absent 



absent 



Eggs in 

 uterus 



numerous 



one 



one 



one 



one ? 



