DEFINITION OF T^INIA NANA. 



657 



GROUP A. Head small, with a single circle of small hooks, seated on 

 an ovoid rostellum. Joints short and broad, even when mature. Genera- 

 tive openings on one side, testes few, a small recep- 

 taculum on the short vagina. Cirrhus-pouch 

 poorly developed. The uterus, a wide cavity ex- 

 tending across the whole joint, and with irregular 

 diverticula. The eggs have two smooth shells, and 

 contain an embryo with somewhat large hooks. 



Subgenus Hymenolepis, Weinland. 



The various species are usually short, and 

 are most commonly found in insectivorous 

 animals. 



Other related forms, usually from herbi- 

 vorous animals, are specially distinguished by 

 the absence of hooks, and by the considerable 

 length of the jointed body. 



Taenia nana, von Siebold. 



Von Siebold und Bilharz, " Zur Helminthographia hu- 

 m&na,,'Zeitschr.f. wiss. Zool., Bd. iv., p. 64, Tab. v., Fig. 18. 



A small tape-worm, from 12 to 20 mm. long, 

 and with a maximum breadth of 0'5 mm. In the 

 anterior third the body is thread-like, but pos- 

 teriorly it enlarges somewhat quickly, so that the 

 last third has an almost uniform breadth. The 

 spherical head has a diameter of about 0*3 mm., 

 and bears, besides the four round suckers (O'l mm.}, 

 a rostellum of O06 mm., whose anterior truncated 

 portion has a single circle of from twenty-two to 

 twenty-eight extremely small hooks. The member 

 of segments amounts to 150-170, of which the 

 last contain thirty or more ripe eggs. The length 

 of the joints is insignificant, and at the posterior 

 end of the worm hardly amounts to quarter of 

 the breadth. The uterus corresponds in form to 

 the joints, and contains numerous eggs of 0*04 mm. 

 in diameter, with embryos of 0'023 mm. 



FIG. 340. Tcenia nana. 

 (x 18.) 



The tape-worm which is here shortly described was discovered by 

 Bilharz in Egypt, and although hitherto observed only in a single 



2 T 



