14 WRIGHT AND MACALLUM. . [Vol. I. 



fact that certain important groups of fibres destined for the 

 caudal lamina have their origin forward on the ventral surface 

 of the body. 



The bulk of the fibres referred to converge on each side into 

 a stout, rounded bundle as they enter into the caudal lamina, are 

 there confined by a series of looped fibres {d, Fig. 4), and then 

 diverge to their attachment on the chief prominence of the 

 muscular processes of each of the large hooks. The other 

 muscles of the hooks are confined to the caudal lamina, the 

 transverse muscle being a strong bundle attached to the small 

 prominence of the muscular process, while the fibres which are 

 attached to the flat, striated shafts originate near the middle line 

 of the lamina, where those destined for opposite sides de- 

 cussate. 



It is obvious that the three sets of muscles described provide 

 for complicated movements of the large hooks ; that those 

 coming from the ventral surface of the body are chiefly en- 

 gaged in "striking;" while those attached to the shaft, when 

 acting alone, can disengage the hooks from the host. The 

 looped fibres, above referred to, can alter the direction of action 

 of the great muscular bundles by approximating or divaricating 

 them as they enter the lamina. Again, it is to be noted that 

 when the caudal lamina is attached, and the body free, the 

 movements of the latter are largely carried out by the ventral 

 muscles described. 



Apart from the muscles of the hooks certain other groups of 

 fibres enter or are differentiated within the caudal lamina, which 

 are chiefly destined for the movement of the suckers. Some 

 fibres from the ventral musculature, instead of entering the 

 rounded bundles attached to the hooks, diverge into the ante- 

 rior margins of the caudal lamina; these must tend to approxi- 

 mate the opposite edge of the lamina, but this is chiefly 

 effected by the strong, transverse bundle which lies directly 

 behind the junction of the body and caudal lamina. On the 

 other hand, the opponents of these muscles are the bands 

 already referred to, which penetrate the dorsal wall of the 

 caudal lamina, and are attached to the convexity of the 

 suckers. 



Concerning the minute structure of the muscle fibre in Trema- 

 todes some few exact statements are to be met with. According 



