90 THE ROYAL SOCIETY OF CANADA 



in the middle line in a small yolk reservoir which opens into the 

 oviduct a short distance beyond the junction of the latter with 

 Laurer's canal. Where it joins the vitelline reservoir the oviduct 

 bends forward and at this point is called the ootype, being surrounded 

 by a mass of unicellular glands, constituting together the shell gland. 

 As it emerges from the shell gland the ootype is very narrow and 

 the muscular walls are strongly developed. It is probable as suggested 

 by Otto (11), that the eggs assume their typical ovoid shape as they 

 move one by one through this narrow passage while the shell substance 

 is still soft. The uterus widens out rapidly from the ootype and 

 forms several loops above the sucker, then runs forward as an irregu- 

 larly coiled canal dorsal to the testes. Just behind the vesicula 

 seminalis the uterus turns to the ventral side and continues to the 

 genital sinus below the cirrus sac. The average size of the mature 

 egg in its shell is • 15 mm. by • 092 mm. The shell is smooth without 

 projections of any kind. Numbers of spermatozoa were noted 

 throughout the uterus and as far back as the junction of Laurer's 

 canal. There is no internal communication between the male and 

 female systems of the worm, probably fertilization is effected by 

 the sperm of another animal. 



Excretory System. 



The excretory pore (Figs. 1,2 & 4) leads by a short canal into 

 a wide excretory bladder with thick, spongy, muscular walls. At 

 its anterior end the bladder gives off two large vessels which extend 

 forward on the right and left sides above the arms of the intestine. 

 I was not able to follow the course of the excretory vessels satisfactorily 

 beyond noting that they appeared only in the dorsal region in the 

 posterior half of the body, while in the anterior half I found coiled 

 tubes of equal size in the ventral region. According to Otto's descrip- 

 tion the dorsal trunks give off medial vessels which unite on the 

 ventral side between the vesicula seminalis and the anterior testis. 



Nervous System. 



Two large anterior ganglia are joined by a commissure above 

 the gut where the pharynx passes into the oesophagus. From the 

 ganglia nerve fibres run forward to the oral end, and on each side a 

 conspicuous bundle of fibres goes backward close to the ventral 

 body wall as far as the posterior sucker. 



The only point in which my observations differ from the published 

 description of the Amph. subtriquetrum from the European beaver is 



