FOEM AND AEEANGEMENT OF THE HOOKS. 523 



meaningless name of Solium and to call the species T. hamoloculata. 

 On the contrary such pouches are always found in the hook-bearing 

 Tcenice, for the hooks never merely project, but always have their 

 roots sunk in the external coverings of the head. After the falling 

 out of the hooks (which often takes place very soon after the removal 

 of the worm from the intestine, and especially if it be placed in 

 water), these pockets are, it is true, less distinct and striking than in 

 Tcenia solium, though this is only the case when the apical region is 

 permeated with a black pigment, as indeed it generally is. In such 

 specimens, the hook-pouches appear as gaps in the pigment, and are 

 very noticeable even on superficial examination. But, on the whole, 

 this pignaentation is less frequently observed in T. solium than in 

 T. saginata. 



The Circlet of Hooks and the Hooks themselves must now receive 

 our attention. 



As in the related forms (with the exception of Tcenia acanthotrias), 

 the circlet of hooks in T. solium is double (Fig. 292) : in other words, 

 although the hooks all have their points on the same circular line, 

 they do not form one, but two successive rows, one anterior to the 

 other. The hooks of the anterior row are larger than those of the 

 posterior, and are fixed to the rostellum somewhat above the 

 lateral border, so that their centre of motion is not so far from the 

 common centre as is the case with the smaller, more peripherally 

 situated hooks. Besides these differences in position, there is also a 

 slight difference in the formation of the roots, for those in front, being 

 situated on a less curved surface, have flatter bases than those behind. 



Fig. 293. — Larger (anterior) and smaller (posterior) hooks of 

 Tcenia solium, ( x 280.) 



The number of and distance between the hooks are the same in 

 both rows, and the smaller ones always occupy the spaces between the 

 larger, so that large and small hooks are in regular alternation. The 

 above-mentioned differences in the size of the hooks depend mainly 

 upon the different lengths of the posterior root-processes, which in the 

 large and small hooks have the ratio of 3:2. But these are not the 

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