68 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 55. 



ined post mortem for parasites in 1913. In view of what we know 

 of the length of life for dog cestodes, it is unlikely that the worms 

 found y»ere present when the dog arrived at Bethesda, Maryland. 

 However, it is possible that the dog was infested with worms of this 

 species and that the worms found were some from infestation due to 

 eating intermediate hosts, presumably fleas or lice, as in D. caninum, 

 which had been infected from the original worms. It is also possible 

 that the infestation origi- 

 nated entirely at Bethesda. 

 A number of specimens 

 were collected at Detroit 

 from dogs Avhich undoubt- 

 edly became infested in 

 that locality. 



Part of the specific de- 

 ; cription is based on von 

 Ratz's illustrations, and so 

 depends for its reliability on the accuracy of the illustrations and the 

 constancy of the features illustrated. 



Fig. bT. — ] >iPYLi- 

 dium chyzeri. 

 Head. E n - 



LARGE1'. AF- 



TF.K VON RAT2, 

 1S97&. 



I'lG. 6S.— I'lPYUniUM CHYZEKI. RCS- 



TELLtTM. Enlarged. After von 

 RAtz, 18976. 



DIPYLIDIUM CHYZERI von Ratz, 18976. 



Specific diagnosis. — Dipylidium: The head (fig. 67) is small, 352 

 to 432 ^ in diameter, and conical. The rostellum (fig. 68) is conical, 

 112 [JL long, and terminates in a rounded tip. 

 There are 13 to 14 circlets of hooks, forming diag- 

 onal rows tovvurd the tip of the rostellum; these 

 hooks are of rose-thorn shape with a flat basal 

 portion attached at an angle. This basal part is 

 formed by a long flat plate, thinned at both ends 

 and bent at the anterior end, and the hook length 

 proper is not over two-thirds the length of this 

 basal portion. The largest hooks are near the tip 

 of the rostellum, where they are 14 pi. long and 

 5.5 ]}. thick; nearer the base they are 10.5 by 5 [j.; 

 and those at the base are still smaller. The 

 strobila is 12 to 20 cm. long and attains its maxi- 

 mimi width, 1.4 to 1.6 mm., near the middle, at 

 which point the segments are almost quadrate. 



( 



Fig. 69.— D I p y l I d I u m 

 CHTZERi. Mature seg- 

 ment. Enlarged. Af- 

 ter VON RAtz, 1897b. 



The free gravid segments are 4.5 mm. long and 



TOO to 750 [J. wide. The genital pores are anterior 

 of the middle of the lateral margin of the seg- 

 ment. The longitudinal and transverse excretory canals are of about 

 the same width. 



Male genitalia. — The testes (fig. 69) are small, 45 to 60 in num- 

 ber, and are scattered at comparatively wide intervals throughout 



