rounded pharynx about 0. 03 mm in diameter and two intestinal trunks 

 which end blindly. The esophagus is practically absent or very short. 

 The excretory system was not observed. The attaching armature of the 

 disc (Fig. 215) consists of 16 edge hooks of the usual form for Poly- 

 stomatidae and of the same length--0. 015 mm. According to the 

 observations of U. A. Strelkov and A. V. Gussew the free-swimnning 

 larva moves relatively slowly and begins to stop rather quickly and to 

 "feel" the bottona of the container. The method of infection of turtles 

 and the further development of N. palpebrae are not known. 



20. The development of Sphyranura Wright 



The structure of the trematodes of the genus Sphyranura, 

 which parasitize the gills of Necturus, is very odd. In addition to the 

 peculiarities of the structure of the sex and digestive systems, adult 

 worms of this genus (Fig. 35) are characterized mainly by the structure 

 of the attaching apparatus. The latter is represented by a well-developed 

 disc bearing 2 powerful suckers, 16 edge hooks, of which two lie in the 

 center of the suckers, and 2 large middle hooks (Fig. 216). 



p. 191 



p. 192 



In 1936 Alvey studied the development of Sph. oligorchis 

 Alvey, although in our opinion not thoroughly enough. The development 

 of eggs took place in the external medium during a prolonged period of 

 time. Alvey removed the developing larvae from the eggs from the 26th 

 day of development and then obtained free-swimming larvae emerging 



01 MM 



Fig. 216. Sphyranura osleri Wright, attaching disc of an adult worm 

 from the gills of Necturus sp. from the Huron River (Michigan, U.S.A. ) 



from the egg on the 27th to the 29th days (Figs. 217 - 218) and finally 

 studied them after attachment. The indications of the author that the 

 larvae are almost completely deprived of ciliary covering are very 

 strange because according to his own observations they are very mobile 

 and swim with the help of their disc (? !). We think that actually the 



207 



