124 



THE CESTOIDEA 



of Tetrarhynchus (33). Each of the two phyllidia, which are dorsal and 

 ventral, consists really of two alae or flaps separated by the projecting 

 edge of the scolex. These four flaps are indeed the four phyllidia, united 



FIG. XVIII. 



1. Echinobothrium affine, Dies., out of Raia, spp. (altered, after Pintner). View of scolex 

 from the side, with the commencement of the body, a, rostellum ; ft, rostellar or frontal 

 hooklets, situated in a dorsal and ventral group of eleven ; in each group there are two kinds 

 six like &J,and five like 6 2 in this species ; at the sides of each group are three small accessory 

 hooklets; 6 ] , fe 2 , the two kinds of frontal hooks of E. musteli, Pintner. The central muscular 

 mass of the rostellum is indicated by dotted lines, but in addition there is a group of retractor 

 muscles of the hooks on each side ; c, one of the ventral phyllidia ; d, e, the right and left dorsal 

 phyllidia, united below ; e, points to the inner face of the phyllidium, the dotted outline indi- 

 cates the lower limit of these organs ; c, d, are in reality separate from one another above, but 

 are represented as overlapping ; /, the long "head stalk" provided with eight rows of spines, 

 characteristic of the genus. In this species there are twenty to twenty-five spines in each row ; 

 /!, one of these spines ; it is quadriradiate, with its fourth spine directed inwards and slightly 

 curved ; g, the uppermost proglottid, which exhibits a notch at each side, indicating, probably, 

 a division into two ; h, the second proglottid. 



2. Transverse section of the scolex, a little above the level of c, in 1 (altered, after Pintner). 

 The parenchyma of the four phyllidia is not indicated ; the longitudinal muscles (as a row of 

 dots) below the cuticle, c, one of the ventral phyllidia ; d, e, the two dorsal phyllidia correspond- 

 ing to those in 1. It is now seen that d and e are in reality separate structures, the body wall 

 intervening between them, where the letter k is placed. The figure '"2" lies in the lateral 

 depressions between c and d k, the retractor muscles of the dorsal frontal hooks ; I, the 

 central muscular mass of the rostellum, formed of transversely arranged fibrillae ; m, the four 

 excretory canals ; n, the great lateral ganglia of the nervous system ; below the rostellar mass 

 they are connected by a transverse commissure. 



3. Plan of the genital organs from below (composed from Pintner's description and figure 

 of E. musteli). In reality the testes would have undergone degeneration before the uterus 

 had attained the size represented, a, Vitellarium ; &, testes ; c, cirrus ; d, genital atrium, which 

 opens on the ventral surface of the proglottid ; e, germarium ; /, vagina dilated in its course 

 to form a receptaculum seminis ; g, uterus. 



dorsally and ventrally (Fig. XVIII. 2). It is a noteworthy 'fact that 

 Pintner could find no calcareous corpuscles anywhere in the tissues of this 

 tapeworm. 



