74 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 55, 



(fig. 78) of rose-thorn shape; the hooks of the most anterior row are 

 the larger, 12 to 15 [i long, and those of the most posterior row the 

 smallest, 5 to 6 )u, long. The hooks are very easily lost and specimens 

 are frequently found without any hooks or with only a few still in 

 place. The suckers are very large and ellipsoidal. The neck is short 

 and thin. The strobila is 15 to 40 cm. long and is composed of 80 to 

 120 segments. The segments are at first very short, then trapezoidal, 

 and finally much longer than wide. Genitalia develop later. Mature 



and gravid segments (figs. 79 

 and 80) have distinctly convex 

 lateral margins, giving the seg- 

 ments the characteristic cucum- 

 ber-seed shape. Gravid seg- 

 ments are 8 to 11 mm. long and 

 1.5 to 3 mm. wide, and are often 

 reddish in color. Genital pores 





C^ 



/ 



/7W- 



?/' V ' 



i/iomm 



Fig. 78.— Dipyudium caninum. Hooks. 



are in the middle of the lateral margin of the segment or at times 

 posterior of this. The lateral excretory canals are quite prominent. 



Male genitalia. — T&stes numerous, 100 to 200 in number, and oc- 

 cupying most of the parenchyma not occupied by the female genitalia. 

 The vas deferens in mature segments extends anteriorly and laterally 

 from the vicinity of the median lobe of each uterus, toward the cirrus 

 pouch, only the final loop extending posteriorly to the cirrus pouch. 

 The cirrus pouch may extend to the longitudinal excretory canal, but 

 is usually entirely lateral of this ; its aperture 

 is dorsal to that of the vagina. 



Female genitalia. — The two lobes of each 

 ovary are very distinct, separated into lo- 

 bules, and loosely formed; they are com- 

 monly said to be wing-shaped, but they are 

 very irregular and difficult to characterize. 

 The vitellarium is some distance posterior of 

 the ovary and is irregular and very loosely 

 lobulate; it is smaller than the median ova- 

 rian lobe, and equal to or smaller than the lateral lobe. The shell 

 gland is between the ovary and the vitellarium. The vagina extends 

 between the two lobes of each ovary and does not dilate to form a 

 receptaculum seminis. The oviduct is dilated to compensate for the 

 absence of a receptaculum seminis. Each egg capsule contains from 

 5 to 20 globular eggs, 43 to 50 fi in diameter, with thin shells and 

 with an onchosphere 25 to 36 n* in diameter, provided with hooks 11 

 to 14 fi long. 



r 



Fig. 79.— Dipyudium caninum. 

 Mature segment, x 12.5. 

 After Neumann in Rail- 

 LIET, 18936. 



