822 DR. F. E. BEDDARD ON A 



49. Contributions to the Anatomy and Systematic Arrange- 

 ment of the Cestoidea. By Frank E. Beddard, M.A., 

 D.Sc, F.R.S., F.Z.S., Prosector to the Society. 



[Received April 30, 1912 : Read June 4, 1912.] 

 (Text-figures 113-121.) 



VI. On an Asexual Tapeworm from the Rodent, Fiher zibethicits, 

 showing a new form of Asexual Propagation, and on the 

 supposed Sexual Form. 



Index. 



Structure 825 



Systematic : 



TJrocystidium gemmipanmi, gen. et sp. n 840 



General Resume and Sj^stematic Position 849 



Anatomical Summary 850 



I received in February of this year two complete tapeworms 

 which were found in the hepatic duct of a Musquash [Fiber 

 zibethicus) which died in the Society's Gardens. The two worms 

 lay together in a part of the hepatic duct just before it receives 

 the bile-ducb, which was much dilated by the parasites. Although 

 these two worms were very diiTerent in appearance, I believe them 

 to be respectively the sexual and asexual form of the same species. 

 I shall give reasons for this conclusion in the course of the 

 following description of the two individuals. 



(1) The Asexual Form. 



The general appearance of this very remarkable worm is 

 shown in text-fig. 113 (p. 824), which illustrates its most 

 remarkable peculiarity, viz., the possession of two series of 

 what appear to be buds at one end of the body. It will be seen 

 in the course of my description of this " Cysticercoid " that it is 

 without any doubt to be regarded as an asexual form. It does 

 not, however, follow that the mature worm found with it is a 

 further stage in its development. On the contrary, indeed; for 

 as a mere matter of guesswork, the assumption would be the other 

 way. Still, I believe that I shall be able to prove that the two 

 worms are stages of the same species, in which event we have the 

 very remarkable fact of both the sexual and the asexual form 

 coexisting in the same host, and, moreover, in a situation where 

 one would expect to meet with sexual forms only. The Hymeno- 

 lepis^ of the mouse is a partly, but not an entirely, parallel 

 instance. 



At first it seems likely, from an inspection of the figure 



