64 



imbedded. When it has attained to a certain size 

 from imbibition (supposing it to be in the interior of 

 a solid organ, and not in any serous cavity), it sur- 

 rounds itself with a capsule or cyst to protect it from 

 external pressure, and to allow of its obtaining the 

 repose requisite for its further development. These 

 cysts constitute an absolutely new formation, which 

 commences round the germ of the vesicular worm, 

 from the same masses of exudation which are depos- 

 ited around the youngest brood during its migration. 

 This new formation acquires a structure analogous to 

 that of the subjacent tissues, and constantly increases 

 in size with the growth of the young cestode vesicle. 



When, however, the young arrive in free cavities, 

 this enveloping cyst is either absent, or, if present, is 

 not developed until a later period, and at a time when 

 the embryo has become a vesicle of considerable size 

 (Kiichenmeister). 



While these embryos are increasing in size from 

 the cause above mentioned, it is seen, that, at the an- 

 terior end, and near the point where the six hooks are 

 situated, a depression occurs, a funnel-shaped pit is 

 there formed, and this gradually penetrates deeply 

 into the body of the embryo. In this pit, the head 

 first makes its appearance, its lateral walls forming the 

 body of the future worm ; and the rest of the vesicle, 

 which is not inverted, becomes the so-called caudal 

 vesicle. That these embryos are really developed 

 into the scolices, is shown by the discovery of Stein, 

 of the embryonal hooks upon the embryos themselves 

 while increasing in size, and also upon the cestoid 



