212 TAPEWORMS OF HARES AND RABBITS STILES. VOL.XIX. 



6. The microscope must supplant the yardstick and internal anatomy 

 must take the place of external form in judging the validity of cestode 

 and trematode genera and species. 



7. The principle of homoplasy must be recognized by helmintholo. 

 gists as well as by other zoologists, and any classification which leaves 

 this important and well-recognized principle out of account can be taken 

 only as a preliminary (although often necessary) study (p. 204). 



8. The median field of the Tseniidie is the seat of the most active lat- 

 eral growth, and the same rule will probably be found to apply to other 

 families of Cestoda. No particular longitudinal zone of the median field 

 can, however, be named as the zone of most active growth in all 

 Ta3niida3 (p. 205). 



9. The armed young cestode which I mentioned in Note 31 [ (1895) is 

 not the young of an anoplocephaline tapeworm, as Curtice, Braun, 

 Kailliet, Neumann, and I had inferred, but represents the young stage 

 of the single-pored cestode referred to in my paper in 1895. 2 It evi- 

 dently belongs to Davainea salmoni. 



10. The double-pored cestode with occasional single pores, described 

 in my paper in 1895, 3 is Cittotcenia variabilis angusta. 



11. I have also found some very young stages of an unarmed cestode 

 in the intestine of the cottontail rabbit, which probably belong to 

 Cittotcenia variabilis. This young stage corresponds to what we may 

 expect to find as the larval form of Moniezia expansa of cattle and sheep, 

 and I doubt whether it will be possible to distinguish it from the young 

 of that species. This renders the question of the origin of the tape, 

 worms of cattle and sheep more complicated than it was formerly sup- 

 posed to be, and demands the strictest experimental proof on the part 

 of any author who suspects that he has solved the mystery of the life 

 history of the cestodes of cattle and sheep. 



12. The head of a cestode increases in size after the parasite 

 reaches its final host, as is shown by a comparison of the younger speci- 

 mens. 



13. None of the adult leporine tapeworms thus far described in Europe 

 have as yet been found in America. The American forms which have 

 been published as " Tccnia pectinata" must be distributed over several 

 species typical to this continent. 



14. The following table includes all of the genera at present recog- 

 nized in the subfamilies Ta3niin, Mesocestoidime, Anoplocephalinse, and 

 Dipylidiinse of the family Ta3niidae. A number of other genera have 

 been proposed, but some of them must fall as synonyms, while judg- 

 ment upon others must be reserved. Several of the genera in this key 



1 Notes sur les Parasites 31: Une phase prdcoce du Teuias <lu Lupin, Bull. Soc, 

 zool. France, XIX, 1895, pp. 163-165. 



2 Notes on Parasites 36: A double-pored cestode with occasional single pores, 

 Centralbl. f. Bakteriol. u. Parasitenk., 1. Abt., XVII. 1895, pp. 457-459. 



3 Loc. cit. 



