18 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.55. 



mordia of the genital organs appear a short distance back of the 

 head; the testes, genital canals, shell-gland, and the main trunk of 

 the uterus are clearly defined before the ovaries and yolk-gland can 

 be detected. The genital pores are irregularly alternate and are es- 

 pecially prominent in segments full of developing eggs, where they 

 may have an antero-posterior diameter of 480 jx, or about one-third 

 the segment length. Calcareous corpuscles abundant, of variable size 

 and shape, and with a maximum diameter of 20 pi. 



3Iale genitalia. — The testes are commonly oval, with long axis 

 paralleling that of the strobila (fig. 15), and are principally confined 

 to two bands along the median side of the longitudinal excretory 

 canals. A narrow band of testes crosses the extreme anterior margin 

 of the segment, connecting the two lateral fields and leaving a large 

 space clear of testes, frequently approximately square in outline, be- 

 tween this band, the lateral testicular fields, and the ovaries. The 

 lateral testicular fields extend to the lateral margin of the ovaries, 

 frequently encroaching on the field of the vas deferens and vagina, 

 and are prolonged posterior of the ovaries to the yolk-gland. The 

 vas deferens arises near the plane of the median stem of the uterus, 

 either on the pore side or the aporal side. At the plane of the ventral 

 excretory canal, or just lateral of this, the vas deferens opens into 

 a tubular cirrus pouch 300 to 370 pi long, with an average length of 

 355 [X. The diameter of the cirrus pouch varies considerably, the 

 maximum diameter being about 110 [x . There is no vesicula seminalis 

 present. The length of the cirrus varies from 418 to 518 pi, with 

 a maximum diameter of about 33 \j. and a lumen diameter of 

 about 8 [X. 



Female genitalia. — The ovaries are elliptical to crescentic in out- 

 line with their longitudinal axes paralleling that of the strobila, and 

 inclose an oval to oblong interovarian fields. The vitellarium is 

 elongated in the transverse axis of the strobila and extends a slight 

 distance between the ovaries but not lateral of them. The shell-gland 

 is very close to the vitellarium. The vagina swings in a wide curve 

 from the genital pore around the nearest ovary and opens into a small 

 receptaculum seminis in the neighborhood of the shell-gland. The 

 uterus originates as a median stem, and develops branches of un- 

 usual form. These branches are club-shaped and so closely approx- 

 imated and at times so united that the ultimate result resembles a 

 lobed sac (fig. 16). In many cases one uterine lobe extends over the 

 longitudinal excretory canals in the vicinity of the genital pore. 

 The eggs are ovoid in shape, are 29 to 37 pi by 27 to 33 pi in diameter, 

 the average being 35 to 31 ix. The shell is about 4 \j. thick. 



Hosts. — Primary: Canis familiaris, Lynx rufiis mwnixmlatus 

 {Lynx rufus maculatus). Secondary: Unknown. 



