160 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 50. 



Leuckart (1867) records some investigations into the life history 

 of what he calls "/S'z'r. spirogyr'us der Waldenmause," apparently an 

 unconscious substitution for jStr. jjolygyrus. He finds that this spe- 

 cies has a rhabditiform embryo. The embryos develop in two to 

 three days and measure 500 ju, in length. The tooth apparatus is 

 weak, so that it is easily overlooked, and exists for only a short time. 

 Possibly correlated with this is the fact that the animal grows only 

 a little during its free existence. In spite of this it remains alive 8 

 to 12 weeks in saliva. The attempt to bring about the further evolu- 

 tion of the worm in its host, the wood mouse, gave what Leuckart 

 i-egarded as a doubtful result. Fourteen days after feeding to a 

 mouse, the mouse was found to contain an extraordinary number of 

 these parasites, but these, if not completely grown, were yet of such 

 considerable size, 8 to 10 mm., that without a control experiment he 

 does not feel warranted in referring them to the feeding. It seems 

 likely, nevertheless, that the feeding was successful. 



It will be noted that in this species, as in //. laeve, Dujardin does 

 not regard the length of the tail and the distance from the anus 



to the tip of the tail as identical. 



HELIGMOSOMOIDES Hall, 

 1916, new^ genus. 



G e n e r i c diagnosis. — Heligmoso- 

 minae (p. 118) : Body commonly coiled 

 in a spiral. Male with filiform spic- 

 ules. Bursa with broad, shallow dor- 

 sal incision. Ventro-ventral and lat- 

 ero-ventral rays divergent, from a 

 counnon trunk, the latero-ventral ray 

 broad and presenting the appearance of a double ray. The lateral 

 rays arise from a common trunk and are divergent (fig. 205). There 



Fig. 205.— HELIGMOSOMOIDES LINSTOWI. 



Bursa. Enlarged. After von Lin- 

 stow, 1878. 



are two dorsal rays with 

 separate origins, their tips 

 located close to the tips of 

 the postero-lateral rays. 

 Between the dorsal raj^s 

 and posterior of the cloaca 

 are 11 small raylike struc- 

 tures terminating in pa- 

 pillae (fig. 206). Two 

 well-develoi^ed prebursal 

 papillae present. The 

 bursa is set on at right 

 angles to the long axis of 

 tlie worm. The vulva is near the head. 



Fig. 2or.. 



Heuqmosomoides linstowi. Bursa. Enlarged. 

 After von Linstow, 1879. 



One ovary, 



