363] PSEUDOPHYLLIDEA FROM FISHES— COOPER 75 



The musculature of the scolex is, as might be judged from its size and its 

 shape, very powerful. While the longitudinal muscles of the neck merely 

 enter the base of the scolex, the transverse and sagittal fibres are directly con- 

 tinuous with the circular and radial fibres, respectively, of the latter. Here, 

 however, the radial fibres are quite separate from the dorsoventrai fibres with 

 which they are considered to be homologous, especially laterally where they 

 pass from the cuticula lining the bothria to the sides of the scolex as in other 

 bothriocephalids with prominent bothrial walls. Farther forward the sagittal 

 muscles proper passing between the bothria are scarce, their function being 

 taken over by the very numerous and closely arranged radial fibres which are 

 quite as plentiful in the median line as laterally. In the terminal disc both 

 transverse and dorsoventrai fibres are again prominent, while the radial ones 

 are absent. Posteriorly the latter pass dowTi along the sharp edges of the 

 beginning of the neck. Frontal sections demonstrate the presence in the edge 

 of the terminal disc as well as in the posterior borders of the scolex of two series 

 of longitudinal arcuate fibres arranged for the control of these prominent ridges. 

 These are perhaps modified portions of the outer longitudinal muscles which 

 are very numerous in the scolex, and converge in the anterior portions of the 

 edges of the .walls of the bothria to become attached to the edge of the terminal 

 disc at the four respective points. 



The chief nerve strands, from 15 to 25m in dorsoventrai diameter and from 

 15 to 20m in lateral diameter, are situated far towards the edges of the medulla 

 and in the median frontal plane or somewhat dorsally (Fig. 83). They pass 

 dorsal to the junction between the lateral and middle thirds of the cirrus-sac 

 and consequently dorsal to the vagina. In the neck they are located in the 

 very borders of the medullary parenchyma, but as they enter the base of the 

 scolex they approach the median line somewhat. As they pass on with a vary- 

 ing diameter towards the tip of the scolex, they give off a number of branches 

 to the walls of the bothria and finally enlarge in the terminal disc to form two 

 ganglia, each with a diameter of about 50m, which send off in turn numerous 

 large branches to the immediate neighborhood. Each of these ganglia is 

 divided into two large trunks which, however, continue only a very short dis- 

 tance farther forward before they are joined by two commissures to their fellows 

 of the opposite side of the scolex in such a way that the two branches of the 

 ganglia on each surface of the scolex are connected. In frontal sections each 

 of these commissures is seen to be bowed slightly forward into the tip of the 

 terminal disc and to give off further forward on each side a large branch which 

 passes farther into the latter. 



The excretory system consists of a varying number of vessels, of which four 

 pursue a more or less constant course thruout the medulla of the strobila. 

 These are found at all levels in transections and are separated from each other 

 in the transverse direction by different distances. The outermost two, how- 

 ever, are slightly larger and have thinner walls than the innermost pa'r. They 

 give off numerous large branches and are connected by various anastomoses 

 with each other and the more peripheral vessels. In the neck they cannot be 



