I IO CHILD. 



work. So far as I am aware, the only account of the develop- 

 ment of this system is the one given by Tower ('oo). 



Liihe ('96) and Cohn ('98) have stated that in Ligula, where the 

 reproductive organs are repeated but the body shows no segmen- 

 tation, and in Schistocephalus, a segmented form, systems of ring- 

 like and radiating transverse commissures connect the numerous 

 longitudinal nerves. The two sets of commissures always occur 

 together, but are said not to be segmentally arranged. Nothing 

 is known, however, of the development of these commissures, and 

 indeed it is not even certain that other nerves do not exist. 



Mr. Tower has very kindly informed me that in abnormal pro- 

 glottids of Moniezia the nervous system was not normally 

 arranged. Unfortunately his notes, drawings, and preparations 

 were destroyed by fire. 



It appears then from the little we know of the nervous system 

 of cestodes, and its development in the proglottids, that the sys- 

 tem of commissures makes its appearance very early in the his- 

 tory of the proglottid. Tower's account of the nervous system 

 in the neck-region of Moniczia renders it very probable that the 

 proglottidal commissures constitute the earliest visible indications 

 of proglottid-formation. As noted above, the nuclei of the cen- 

 tral parenchyma in the neck are more abundant in the region of 

 the lateral nerve-cords and in a dorsal and ventral layer which 

 corresponds closely in position to the region occupied by the 

 dorsal and ventral parts of the nervous system. Each proglottid 

 begins to form in two separate parts, one in the region of each 

 lateral nerve-cord ; these two parts extend toward the center and 

 unite, /. c., they follow in general the same course of develop- 

 ment as do the dorsal and ventral transverse commissures (Tower 

 'oo, Fig. i, Taf. 21). A little later the process of proglottid- 

 formation extends to the peripheral parenchyma ; the small 

 nerves extending toward the surface of the body appear, accord- 

 ing to Tower, somewhat later than the commissures. Still later 

 in the history of the proglottid the genital organs appear. Tower 

 found certain nerves which he designates as genital nerves, and 

 states that these appear later than the other portions of the nerv- 

 ous system. All of these facts certainly indicate a close connec- 

 tion between the development of the nervous system and that of 

 the proglottid. 



