146 TAPEWORMS OF HAUES AND RABBITS STILES. VOL.XIX. 



cestodes Avhich had accidentally gained access to rabbits, or did there 

 exist in American rabbits an adult cestode belonging to the genus 

 Davaineaf 



The relation of the subject to the tapeworms of cattle, sheep, and 

 horses made it absolutely necessary from an economic standpoint, and 

 the relation of these forms to the adults in rabbits made it desirable 

 from a scientific standpoint, to immediately revise the adult cestodes 

 found in rabbits. This work was accordingly begun, and in 1895 my 

 paper 1 was published announcing the finding of a double-pored cestode 

 with occasional single pores, and the occurrence in American rabbits 

 of a single-pored cestode with a Davainea-lik& uterus. 



This paper practically disposed of the young armed cestode of rabbits, 

 for after reading it the natural conclusion of every helmiuthologist 

 would be that this parasite was probably a Davainea and that we were 

 no nearer the solution of the question as to the young form of Moniezia 

 than we were before. 



The present paper is the result of the revisional study mentioned 

 above. In it I finally dispose of the armed form mentioned in 1894, 

 and at the same time I am obliged to complicate the question as to the 

 larval stage of Moniezia still further by presenting an unarmed young 

 cestode in rabbits. I further give an anatomical systematic revision of 

 the adult leporine tapeworms, together with their generic relationship 

 to the cestodes of cattle, sheep, and horses. 



I desire to call particular attention to the young unarmed cestode de- 

 scribed on p. 201. Had any worker found this parasite in an insect, 

 worm, or snail in a locality where cattle and sheep are infested with 

 Moniezia expansa, he would hardly have hesitated to announce the dis- 

 covery of the intermediate host of this important parasite. The find- 

 ing in one host of a larval form whose head resembles a certain adult 

 in another host does not, however, scientifically establish the life history 

 of that particular parasite, 



I can now prophesy confidently that it will be almost, if not entirely, 

 impossible to distinguish the larval stage of M. expansa from that of a 

 dozen or so of other tapeworms, and on account of the great economic 

 importance of this question I caution against any too early and too 

 ungrounded announcement of the source of infection of cattle and sheep 

 by this species. The only work upon this subject which will be worthy 

 of full credence is experimental feeding. 



Within recent years it has been customary to associate the larvae 

 found parasitic in some animals with the adults parasitic in other hosts 

 simply because of a similarity of the heads and hooks. This is par- 

 ticularly the case with the avian tapeworms. I feel it necessary to enter 

 a protest against carrying these generalizations too far, for at present, 

 when so many of the adult avian parasites are so incompletely described 



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

 Centralbl. f. Bakter. u. Parasitenk. . 1 Abt.. XVII, 13-14, pp. 457-459. 



