294 ENTOZOA. 



escapement as a normal condition of things. I believe Schubart 

 and Yon Siebold were among tlie first to observe tlie ciliated cha- 

 racter of the Bothriocephalus-embryos ; but these organisms have 

 since been very carefully studied by several observers. The 

 embryos present a remarkably attractive appearance, in consequence 

 of the unusual development of the cilia, combined with the general 

 transparency of the other embryonic coverings. There are, in 

 point of fact, three distinct membranes ; an external one bearing 

 the cilia, an intermediate one forming the capsule of the embryo, 

 and an inner integumentary membrane, proper to the six-hooked 

 embryo itself. Through aU these coverings, the six boring-hooks 

 are easily seen, situated near one pole of the body ; aU of them 

 resemble one another, but in other respects they conform to the 



Pig. 64 — Six-hooked embryo escaping from its oiKated eoTeriug. — Leuckart. 



characters ordinarily exhibited by the cestode proscolices. Accord- 

 ing to Knoch, the hooks are about the same length as the ciha ; 

 but Leuckart has shown that this is an error, the cilia being at 

 least three times longer than the hooks. After the disappearance 

 of the ciliated covering, the last-named observer had occasionally 

 noticed certain natural movements of the hook-apparatus, from 

 which, of course, it might be inferred that the embryos were alive 

 and ready for their passive transference into the body of some 

 intermediate host. What this particular kind of host may happen 

 to be is not yet satisfactorily determined. Knoch, indeed, would 

 have us to beheve, that in the case of Bothriocephalus latus there 



