HISTORICAL SKETCH OF OUR KNOWLEDGE. 



715 



It was then established by Bertolus and myself that the ciliated 

 embryos of Bothriocephalus latus, like those of other forms since dis- 

 covered, serve just as do the similarly 

 ciliated embryos of Distomum for 

 enabling the free embryo to migrate 

 into a temporary host, in which the 

 further development to a cysticercoid 

 intermediate form occurs. This, of 

 course, suggested aquatic animals, 

 having the same habitat as the free- 

 swimming embryo. That fishes were 

 thought the most likely subjects is not 

 surprising, since these are not only the 

 most frequent prey of all aquatic 

 animals, but also because in the flesh 

 and viscera of fishes Cestode larvse had 



not unfrequently been found encap- °f ^''«A'^«^^««»» ^«««»- (x 600.)" 

 suled, which, from the structure of their heads and other organs, might 

 be young stages of Bothriocephali. In fact, Bertolus did not hesitate to 

 claim as the intermediate form of B. latus one of these larvae described 

 by Eudolphi as Ligula nodosa, and parasitic in various Salmonidae. 



The reasons which Bertolus gave for his opinion were, indeed, 

 scarcely sufficient to establish the connection of the two forms ; and that 

 the less since Ligula nodosa is a parasite of a very debateable character. ^ 

 We were, however, led to attempt a solution of the problem experi- 

 mentally. For this purpose, with the consent of the owner, I put a 



Fig. 374. — Free-swimming embryo 



large quantity 



of ova and free-swimming 



embryos, enough to infect hundreds of fish, 

 into a trout-stream^ near my home, then in 

 Giessen. The result was unfortunately nega- 

 tive, all the trout which I examined — in all 

 more than two dozen — at various intervals up to 

 two months after the introduction of the em- 

 bryos, were free from the expected parasites. 

 Similar experiments on certain species of 

 Cyprinus also failed. The fact, which I then 

 learned, that Botticher had, in a post mortem 

 examination of a woman who had died in poor circumstances at" 

 Dorpat, and who had for weeks before her death eaten neither fish 

 nor flesh, found almost a hundred Bothriocephali, which, except one 

 about a yard long, only measured a few inches, and must therefore 



* Diesing regards it (" EeTision der Cephaloootyleen, Abtheilung Paramecotyleen," 

 d. k. Wiener Acad., Bd. xlviii., p. 232) as a separate portion of Trianophonts. 



Fio. 375.— Encapsuled 

 larva of a Bothriocephalus 

 from the smelt. ( x about 

 20.) 



' First German edition 



