2 PEOCEEDINGS OF THE NATIONAL MUSEUM vol. 74 



mounted in toto and examined from head to terminal segment. It is 

 no small task to examine a large cestode in this way, for the number 

 of segments present in each worm examined varied between 1,136 and 

 2,118 in the M. expansa group, and 758 and 1,462 in the M. planissima 

 group. Twenty complete worms, selected because they showed the 

 most varied naked eye appearance, and as many more portions of 

 worms were examined in this way. 



It is proposed to mention a number of the characters used in 

 definitions of the species of the genus Moniezia, and to show that 

 extremes of size and shape are joined by a more or less regular series 

 of intermediate modifications. 



In examining the descriptions of members of this genus the writer 

 has found only six definite specific characters, which may be stated 

 as foUows: The interproglottidal glands may be absent, as in M. 

 alba (1). When present they may be of the linear type, as in M. 

 planissiTna (2) , or they may be of the saccular type, as in M. expansa 

 (3), or, according to Sauter, both types may be present in one worm, 

 as in M. conjugens (4) . The testes instead of being in one band may 

 be arranged in two triangular areas, as in M. trigonophora (5). 

 The uterine folds usually pass only on the dorsal side of the longi- 

 tudinal excretory vessels, but they may pass both dorsally and ven- 

 trally, as in M. pallida (6). 



Apart from these six characters, specific identity appears to de- 

 IDend upon a number of more or less slight variations, among which 

 the following may be mentioned as the more important: 



1. Shape and direction of the suckers, and shape of head. 



2. Color and translucency of the strobila. 



3. Length of the worm and the number of segments present in the 

 strobila. 



4. Size of the largest segment. 



5. Width of the head. 



6. Length of the neck. 



7. Distance from the head at which the first genital primordia 

 appear. 



8. Distance from the head at which the first testes may be seen. 



9. Number of testes present in each segment. 



10. Interproglottidal glands, their number to the segment in the 

 M. expansa group, and their length in the M. planissima group ; and 

 whether distinct or only faintly visible. 



11. Position of the genital pore. 



12. Size of the eggs. 



1. From the study of the writer's material and of descriptions and 

 drawings of the various species, the differences in the shape of the 

 head seem to be no more than could easily be explained by the plastic 



