HISTOKICAL SKETCH OF OUR KNOWLEDGE. 



715 



FIG. 374. Free-swimming embryo 



It was then established by Bertolus and myself that the ciliated 

 embryos of Bothrioceplialus 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 larvae had 



r* ,1 , p , of Bothriocephalus lotus. ( x 600.) 



not unirequently been round encap- 

 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 

 large quantity of ova and free-swimming 

 embryos, enough to infect hundreds of fish, 

 into a trout-stream 2 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 from the smelt 

 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 



1 Diesing regards it (" Revision der Cephalocotyleen, Abtheilung Paramecotyleen," 

 Sitzungsb. d. Tc. Wiener Acad., Bd. xlviii., p. 232) as a separate portion of Tricenophorus. 



2 First German edition of this work, Bd. ii., p. 867. 



FIG. 375. Encapsuled 

 larva of a Boihriocephalus 

 (x about 



