44 A FAUNA WITHIN ANIMALS. II. 



strongly muscular, and when contracted, is short, thick, and transversely contorted, 

 and curves forward to the position of the generative aperture and the sperm atheoa, 

 or when elongated, is narrow, relatively twice as long as in the other case, doubled 

 upon itself, and first proceeds backward and then forward to the spermatheca, and is 

 smooth. Its canal is narrow, closed when at rest, and is capable of transmitting 

 but a single egg at a time. 



The spermatheca (/), is a large oblong or long ovoid receptacle, situated ventrally 

 and anteriorly to the generative aperture, and is connected at its posterior extrem- 

 ity by the termination of the uterus and commencement of the vagina, which con- 

 join at an acute angle to each other. 



The vagina (g) curves downward, and terminates in an infundibuliform generative 

 aperture, surrounded by a thick prominent lip (hj PI. VI. 1, g). The parietes of 

 the vagina are thick, strongly muscular, and transversely contorted. 



The ripe ova are oval (PI. VII. 14, c). The young Ascarides (22) have the same 

 form as the parents. In them, the generative apparatus is entirely undeveloped. 



The testicles (16, V) of the male are long, cylindroid, lobed organs, one upon each 

 side of the posterior part of the intestinal canal, filled with oval sperm atophori (18). 



The spiculae of the penis (19), are equal, scimetar-shaped, and are protruded 

 immediately posterior to the anal aperture (17, c). 



3. DESCRIPTION OF THE GENUS AND SPECIES OF HYSTEIGNATHUS. 

 IIYSTRH-JVV TIH *, LEIDY. 



Body cylindroid, rigid, finely annulated ; anterior annulations, excepting the first, 

 furnished at their posterior margin with simple spines divergent backward. Oral 

 annulus a truncated cone; mouth round. Tail pointed. Buccal organ long cylin- 

 drical ; gizzard pyriform. Generative aperture of the female near the middle of 

 the body. Ovum oval. 



* 



Hystrignathiis rigidus, LEIDY. 



Proc. Acad. Nat. Sci., Phila., v., 102. 



(PLATE VII. 8-10.) 



Female. Body straight, rigid, elastic, cylindrical, white, translucent ; anteriorly 

 and posteriorly narrowed; anterior 106 annuli, extending a short distance posterior 

 to the position of the commencement of the ventriculus, furnished at their posterior 

 margin with 16 simple, conoidal, divergent spines ; anterior spines equal in length 

 to the width of the annuli, the posterior decreasing to mere points; posterior annuli 

 of the body indistinct. Oral annulus deeply truncated, conical, naked. Mouth large, 

 round; pharynx extending through the first two annuli; buccal organ (PI. VII. 9, a) 

 cylindrical, rounded at the extremities, extending through 56 annuli ; gizzard (b) 

 pyriform, with a cylindrical neck, narrower than the buccal organ, and a spherical 



