138 0)1 a Coenarus in the Rat 



The guard of the large hook is triangular in shape in lateral view, 

 with its maximum diameter at the base. The free end of the guard is 

 usually pointed. 



The small hooks are from 90 /^ to 105 /x in length. The blade is mode- 

 rately to well curved. 



The handle is quite thick and long. It is very slightly tapering at the 

 distal extremity, is bent somewhat dorsally, and its axis meets that of the 

 guard at an angle of from 100° to 110°. 



The face view of the guards of both large and small hooks is broad, 

 though the guard of the small hook is wider than that of the large hook. 

 Each of these guards has tapering edges and a median groove but is not 

 bifid. 



The hooks of the Coenurus of the rat, of Coenurus cerebraUs, and of 

 Coenurus serialis, appear to be formed after the same type. Both the 

 large and the small hooks are about the same size in all. The small hooks 

 of the Coenurus of the rat and Coenurus cerehralis are much alike in their 

 chief features, but that of Coenurus serialis differs rather markedly 

 from these in the character of the handle. In the large hooks of all, the 

 handle, blade and guard are well developed. In all the handle is straight 

 in its general direction. The blades of all the large hooks are moderately 

 curved. Nevertheless more detailed examination of my material showed 

 that the hooks, both large and small, of each Coenurus possess some fea- 

 tures in which they differ from the hooks of any other Coenurus, though 

 in some cases the difference may be only one of degree. 



In the material examined which consisted of one cyst from the rat, 

 one cyst of C. cerehralis, and two cysts of C. serialis, each scolex of the 

 Coenurus from the rat bears 24 to 28 hooks. Each of three scolices of 

 Coenurus cerehralis bears 26 hooks, while each scolex of Coenurus serialis 

 bears from 26 to 30 hooks. Hall, 1919, says that a scolex of Coenurus 

 cerehralis bears from 22 to 32 hooks, and one of Coenurus serialis bears 

 from 26 to 32. Thus the number of hooks in each scolex is about the same 

 in the three Coenurus; viz. the Coenurus from the rat, C. cerehralis, and 

 C. serialis. 



The large hooks of the Coenurus from the rat are from 130/li to 145/x 

 in length; those of C. cerehralis from 145 /x to 165 /a and those of C. serialis 

 from ] 35/i to 1 45/Lt. So that here the large hooks of 6'. cerehralis are longer 

 than those of the Coenurus of the rat and C. serialis. Hall gives the length 

 of the large hooks of C. cerehralis as from 150 ju, to 170 fi and the length of 

 those of C. serialis as from 135 yu, to 175yLt. In this case some of the hooks 

 of C. serialis are longer than those of C. cerehralis. 



