380 WM. L. TOWER, 



present paper, though it may be an open question whether the slight 

 accumulation of ganglionic cells in these regions warrants giving them 

 the dignity of ganglia. However, in those cases where the nerve 

 elements are compacted, these ganglia present a structure not unlike 

 that of the other ganglia of the nervous system. 



The dorsal and ventral longitudinal nerves give off lateral branches 

 along their entire length, which lie in the layer of the longitudinal 

 muscles. Fig. 14 (PI. 23) shows one of these nerves (the right dorsal) 

 which is more compact than usual. In the region of the two branches 

 there are ganglionic cells. 



It gives me pleasure to acknowledge my indebtedness to the 

 director of the Zoological Laboratory, Dr. E, L. Mark, for his kindly 

 critericism and many helpful suggestions given me during the progress 

 of my work. 



Cambridge, Mass., Sept. 1, 1897. 



Postscript. Since this paper was written Cohn (in : Zool. Jahrb., 

 V. 12, Anat., 1899, p. 425—76), has published his studies on the 

 nervous system of several Cestodes. He believes that all of the 

 longitudinal nerves, together with their transverse connections in 

 both scolex and proglottides, constitute the central nervous system. 

 The branches from these to the various organs and to the surface of 

 the animal he regards as the peripheral system. 



From the conditions that I have found in Moniezia I believe 

 this division to be justifiable, and that there is a true central nervous 

 system in Cestodes. I do not, however, agree with Cohn's view that 

 the "main commissure" is a mere connective. I find in Moniezia that 

 there is a well developed pair of central ganglia in the scolex. These 

 ganglia possess ganglionic cells which send nerve fibres to other parts 

 of the nervous system of the scolex, and posteriorly to the proglottides. 



Since this paper was written I have studied further the nervous 

 system of Cestodes, using with some success methylen-blue and Golgi 

 impregnations. I find a distinct central system in the scolex, which 

 I think may function as a central coordinating center — a brain. The 

 rest of the central nervous system is comparable to a longitudinal 

 nerve chain. The conclusions reached in this i)aper as to the paths 

 taken by the fibres in the cephalic ganglion were substantiated by 

 my more recent methylen-blue and Golgi preparations. 



