OF THE CYSTIC ENTOZOA. 81 



tached to it ; but that the other is quite free and almost trans- 

 parent. This transparent part was that originally attached to 

 the parent or germinal membrane ; and the shreds are conse- 

 quently the remains of the internal membrane of the parent. 

 Shortly before the young hydatid separates from the germinal 

 membrane of the parent, smaller cells are seen within it, which 

 increase in size along with it. These are another generation of 

 hydatids, and the fourth in the series I have been describing. 



About this period in the process of developement, there may 

 be seen in some forms of hydatids of the tertiary growth, a dark 

 irregular flat nucleated spot, which always occupies the same 

 place, immediately opposite that of attachment. This spot is vi- 

 sible only before the separation. I am inclined to consider this 

 spot as the first appearance of the pedicle, or what is generally 

 termed a head in the class. This species I denominate Acephalo- 

 cystis armatus. This appearance is merely the nucleus or central 

 cell, from which all the others are produced ; thus illustrating that 

 the pedicles of Csenurus and Cysticercus are analogous to this 

 nucleus, both being reproductive organs ; in the acephalocyst 

 being a reproductive organ only, in Csenurus and Cysticercus 

 being chiefly a reproductive organ with a slight adaption for the 

 purposes of prehension. 



If the small cells which are seen in the tertiary hydatids are 

 the young, they must be the first of those which are afterwards 

 seen attached to the germinal membrane, for I have not met 

 with secondary hydatids enclosing separated young individuals. 

 It is only after the hydatid has obtained a nidus, or separate 

 habitat of its own, that it begins to throw off its young from the 

 germinal membrane, and those only which had been formed dur- 

 ing the tertiary and secondary periods. Thus, if the original 

 hydatid is buried deep in the textures of the infested being, or 

 from other causes is prevented giving exit to its young, (for it is 

 by the dilatation caused by the young within it that the parent 

 sac gives way,) it soon becomes unable to extract proper nourish- 

 ment from the infested being, the young within it become de- 

 composed, and the whole animal degenerates either into a firm 

 cicatrix, or, as is most general, into a fatty cretaceous matter. 



F 



