MORPHOLOGY OF CESTODES FROM POULTRY 



33 



the cyst between the base of the neck and the attachment of the 

 bladder, while the other two pairs of hooks are located in the 

 bladder. 



The cavity of the bladder is formed apparently by a splitting 

 or hollowing out of the cells of the tail, because the wall is con- 

 tinuous and of the same histological structure. The wall of the 

 bladder is constructed of two layers, an inner cell layer and an 

 outer cuticular layer. The outer cuticular layer is more or less 

 striated on account of minute fibrils uniting it with the inner cell 

 layer. Histologically, the structure of the inner layer is con- 

 structed of somewhat granular substance arranged in fibers form- 

 ing a network which encloses clear spherical cells with large nuclei 

 (Fig. 13). Outside of the cuticular layer is located the peritoneum 

 of the host which lies upon the bladder and surrounds it as well 

 as the cyst. 



C. COMPARISON OF ADULT AND CYSTICERCUS 



A comparative study of the adult and the cysticercoid shows 

 the likeness which exists between them. The presence of the 

 same number of hooks, having exactly the same size and shape 

 as seen by comparing Figures 8 and 9. Minute booklets of the 

 same size are present in both cysticercoid and adult lining the suck- 

 ers, the entire surface of the scolex and a part of the neck region. 

 Rosseter (1891: 365) shows that the hooks on the rostellum and 

 suckers of Echlnocotylns Rosscteri undergo no changes during 

 the act of transition from cysticercus to adult stage. The rpstellar 

 sac is of the same general shape in both. The head of the rostel- 

 lum is not expanded in the cysticercoid as in the adult because it 

 has not functioned as yet. This corresponds to figures as shown 

 by Schmidt (1894. PI. VI, Fig. A) of the cysticercoid and Krabbe 

 (1869, Fl. VI, Fig. 114) of the adult of Drepanidotmiia anatma, 

 and by Grassi' and Rovelli (1892, PI. IV. Fig. 7, 8) of the cysti- 

 cercoid and Blanchard (1891: 16) of the scolex of Davainea 

 proglottina. No measurements are given for the rostellum of 

 either the cysticercoid or the adult by the above authors. 



There is a great deal of difiference in the size of the scolex 

 between the cysticercoid and the adult. In my specimens the 



