BOTHRIOCEPHALUS LATUS. 293 



bart, Leuckart, and Knocli. From the asseverations made in a 

 magnificent-looking brocliure recently issued by the last-named 

 author, and especially from previous statements pubHshed by this 

 observer (" Petersburger medicinische Zeitschrift," 1861, No. 3) 

 one was, in the first instance, led to believe that the whole mystery 

 had been cleared up, but on looking closer into the matter, it un- 

 fortunately turns out that there are still many hnks wanting to 

 complete the chain of evidence, and that Knoch's conclusions are 

 in many respects erroneous. Whilst waiting patiently for the 

 " missing Hnks," we may, in the meantime, rely upon the correct- 

 ness and importance of the following ascertained facts : — 



The dark-brownish coloured eggs, which, from their oval figure 

 and lid-Hke operculum at one end remind us of the ova of the 

 common fluke, do not appear to be capable of developing an 



Fia. 63. — Two examples of the egg of BothnocepTialus labus ; the upper one showing a finely seg- 

 mented yelk, which, in the lower specimen, has escaped (x 250 diam.) — Leuotart. 



embryo in their interior, until they have escaped from the parent 

 and have been immersed in water for a period of from four to 

 eight weeks. More or less speedily, after the expiration of this 

 variable period, the opening of the lid permits the escape of a fully 

 developed ciliated embryo, which, after the rotatory fashion of 

 Volvox, swims about for several days — from four to six, according 

 to Knoch— whereupon, the ciliated covering bursts, so as to allow 

 of the escape of a six-hooked, non-ciliated embryo. In Knoch's 

 opinion this bursting of the ciliated covering is to be regarded as 

 a sign of miscarriage on the part of the embryo ; but, with more 

 show of probabihty, Leuckart, on the other hand, regards this 



