90 OF THE ANATOMY AND DEVELOPEMENT 



after a time become themselves independent pedicles. The cells 

 within the pedicle are arranged regularly in the form of concen- 

 tric circles, each cell as it becomes a parent forming a centre. 

 The latter, or distal portion of the pedicle, contains very few, if 

 any, of these cells, but bears on its extremity a double series of 

 bent barbed teeth, which enable the animal to attach itself firmly 

 to the infested body. Four suckers are also placed at regular in- 

 tervals round the sides of this portion of the pedicle. 



When one of the smaller cells escape from the pedicles, and 

 obtains a situation between the layers of the parent sac, it shortly 

 commences to take on a new action, the nucleus enlarges and 

 presents a clear spot in the centre. As this spot encreases in 

 size, the nucleus becomes irregular on its edges, and shortly be- 

 comes nodulated, each of which nodules after a time are thrown 

 off as separate cells, a central cell occupying the place of the 

 clear central spot.* 



This is the termination of the first stage of the developement 

 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 

 developement. 



After numerous circles have been thus formed, the cells 

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

 come 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 

 developement 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 charac- 

 ters resemble so much both those of Acephalocystis and Csenurus 

 that I have not yet been able to decide with precision to which 



* It will be noticed by all observers, the great similarity which exists between the develope- 

 ment of this animal and the mammiferotis ovum, as described by Dr. Martin Barry. 



