488 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



to naturalists. Tliis animal is composed of a double sac 

 from the external surface of which proceed a number of small 

 bodies, termed pedicles. These pedicles are contained between 

 the two membranes of the sac, project at right angles from 

 its surface, and are armed at the extremity with a double 

 circle of teeth. 



The sac of the Ctenurus is composed of two membranes, 

 the outermost of which acts as an organ of defence, the 

 internal, containing a layer of absorbent cells, acts along with 

 the larger cells contained in the pedicles as organs of 

 nutrition. The natural size of a pedicle is about the one- 

 eighth of an inch in length. It is divided into two parts, the 

 basal and distal. The former contains the absorbing cells 

 already spoken of, which, after a time, become themselves 

 independent pedicles. The cells within the pedicle are 

 arranged regularly in the form of concentric 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 

 intervals 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 increases in size, the nucleus becomes irregular on its 

 edges, and shortly becomes nodulated, the 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 develop- 



* The great similarity which exists between the development of this animal 

 and tlie mammiierou.s o\iuu, as described by Dr. Martin Barry, will be 

 noticed by all observers. 



