THE CYSTIC ENTOZOA. 489 



ment of the ovum, after which the nucleus of the central cell 

 undergoes a similar process, the cells proceeding from it 

 pushing out nearer to the circumference those of the previous 

 generation. Thus we have a great series of centres, round 

 which all the other cells are arranged in circles. This I have 

 termed the discoidal period of development. 



After numerous circles have been thus formed, the cells 

 nearest the circumference, and, of course, those first formed, 

 become parents, and consequently centres ; but a few of these 

 gaining the advantage, dissolve the more peripheral cells and 

 absorb them, thus becoming principal centres. As soon as 

 this change in the development has taken place, the mode of 

 growth, hitherto discoidal, becomes vertical, or at right angles 

 to the sac, and so proceeds until the pedicle becomes perfect. 



There is still another animal belonging to this series, and 

 which requires to be noticed in this place. It is nondescript, 

 and its characters resemble so much both those of Acepha- 

 locystis and Csenurus that I have not yet been able to decide 

 with precision to which genus it belongs. It has certainly 

 more of the characters of the Csenurus than Acephalocystis, 

 although many also connect it most intimately with the 

 latter. In the meantime, however, I have placed it along 

 with Csenurus, and from its habitat called it C. hepaticus. 

 In all its more important characters, it is very similar to the 

 C. cerebralis. 



VI. OF CYSTICERCUS. (PLATE XII) 



Cysticercus is distinguished from Caenurus by its sac 

 having only one pedicle ; it is also always contained in a cyst, 

 which, in some cases, is formed from the compressed textures 

 of the infested animal, while in others it consists of two mem- 

 branes, viz., one similar to that mentioned, and another, sui 

 generis, and belonging entirely to the parasite. The pedicle 

 of the Cysticercus is exactly similar in its structure to that of 



