206 TAPEWORMS OF HARES AND RABBITS STILES. 



Iii Cittotcenla marmotce (Plate XI, fig. 5), C. prcecoquis, and C. pecti- 

 nata (Plate XVI), on the other Land, there also is a marked lateral 

 growth between the ovary and the ventral canal while the lateral field 

 remains nearly the same width throughout the entire length of the 

 strobila. In C. variabilis (Plates XIX-XX) there is a marked growth 

 in the lateral fields. 



Abnormalities in the segments. Eiehm has already recorded segments 

 of Ciitotcenia denticulata with three sets of female glands, and I have 

 recorded segments of C. variabilis angusta with a single pore. New 

 cases of both of these variations have been noticed in the preparation 

 of this paper, namely, triple sets of female glands in C. denticulate 

 and single pores in C. variabilis. I can look upon these cases, however, 

 only as variations, similar to the occasional double pores in Bothrioceph- 

 alus latus and Thysanosoma (jiardi, and can not ascribe to them any 

 particular value from a systematic standpoint. 



The value of the genital pores in classification. Objection has arisen 

 in some quarters to adopting the genital pore as the basis of classifica- 

 tion. I both agree and disagree with this objection. It must not be 

 forgotten that when Blanc-hard used the genital pores as basis for his 

 classification, he naturally used the pore as representative of the geni- 

 tal system; thus, if the pores are single, the entire female system is 

 generally single; if the pores are double, the entire system of female 

 glands is generally double. Viewed from this standpoint (which is the 

 only logical interpretation I can give to Blanchard's classification, pro- 

 posed in 1891), I must insist upon the great value of the pores in classi- 

 fying cestodes. At the same time I fully agree and have stated so 

 more than once before that the pores un associated with other charac- 

 ters can not be relied upon as basis for a natural classification of 

 cestodes. Internal topographical anatomy must, in my opinion, form 

 the basis of the natural classification for both Oestoda and Trematoda. 

 The size and form of the segments are characters which we should use 

 with the greatest caution, always making due allowances for technique 

 and contraction ; as generic characters I can under no circumstances 

 admit their validity, and must therefore reject Sonsino's recently pro- 

 posed genus Panceria (based essentially upon double pored segments 

 which are longer than broad) unless other characters are brought for ward 

 to place the genus on a firmer footing. 



In systematic work in helminthology we must not lose sight of another 

 principle which is well acknowledged in other specialities, namely, that 

 a given character which may be of great importance in classifying the 

 species or genera of one group does not necessarily hold as a taxo- 

 nomic character in all genera or higher groups of the same order or 

 class. Thus the unilateral! ty of the pores in Hymenolepis and Anoplo- 

 cepliala appears, so far as investigations have gone, to be a very impor- 

 tant and constant character, while the same character must be used 

 with the utmost precaution in the genus Davainea. I have shown 



