no 



THE CESTOIDEA 



The nervous system of Bothriocephalus (Fig. VIII.) consists of a 



right and a left longitudinal 

 cord traversing the strobila 

 throughout its length, lying 

 nearer to the middle line than 

 to the margin. In the scolex 

 they are united by a " cerebral 

 commissure," containing gan- 

 glion cells, whence four nerves 

 pass back along each side of 

 the scolex. The nervous sys- 

 tem in the Merozoa generally 

 agrees with this simple type ; 

 there is always one, sometimes 

 two, marginal nerve cords, 

 which are, in several instances 

 at least amongst the higher 

 forms, united by a transverse 

 or circular commissure near 

 the hinder margin of each 

 FIG. VIIL proglottid (Tower (47), and 



Bothrioceph. latus, L. Plan of the nervous Others). A Superficial net- 

 system of the scolex (altered, from Niemec). a, -iirrirlr nf nprvp fihrpc ic in rrm 

 one lateral nerve which extends throughout wor f 



the entire strobila ; &, the two lateral accessory nection with these main COl'ds 



nerves of one side ; c, one dorsal and one ventral /-p, , >. 



accessory nerve of one side; e, the incomplete (-DlOCnmannj. 



circular commissure connecting the main nerve T f ^ o Pn W tliP pnrrlc QT-A 



and the accessory nerves, c ; /, the anterior nerves ; 



g, one bothrium- h, the transverse ganglionic always Connected by a tranS- 

 comnnssure (brain), in front of which is a small f 



additional commissure. verse cerebral commissure, and 



usually there are one or even 



two accessory, circular connections, whence more or less numerous 

 nerves are given off (Fig. IX.). The degree of complexity of this 

 apparatus is connected with the development and needs of the 

 organs of the scolex, and appears to have no systematic value 

 (Niemec, 31). 



The most important of the internal organs from the system- 

 atist's point of view are the genital organs ; these in B. latus are 

 fully developed in about the 600th proglottid, which is therefore 

 said to be " mature." On the ventral surface of such a proglottid 

 two pores lie in the median line ; the anterior pore is the opening 

 of the genital atrium into which open the male copulatory duct 

 or penis, and the female copulatory duct or vagina, the posterior 

 aperture is the " birth-pore " or opening of the uterus (Fig. III. 4). 



In the youngest proglottids, immediately following the head, 

 no trace of the genital organs occur ; but as the proglottids grow 

 older, and become further removed from their point of origin, the 

 forecasts of the organs make their appearance, the male organs 



