No. 6.] THE CESTODE MONIEZIA EXPANSA. 265 



here can be distinguished by the fact that at one edge or the 

 other or both the corresponding furrows on the two surfaces do 

 not meet. That some distortion has also occurred in this case 

 is probable from the fact that in the regions immediately out- 

 side and posterior to that of the figure otherwise normal seg- 

 ments are oblique dorso-ventrally, as if the dorsal surface had 

 moved posteriorly over the ventral, or the ventral anteriorly 

 over the dorsal. The segment b is bounded by a furrow begin- 

 ning at d" and forming a spiral of nearly two turns, ending 

 free on the ventral surface (e'). The genital organs b', on the 

 left side of b, lie almost between the dorsal furrow e and the 

 ventral d' t and it is the only genital mass on the left for 

 the whole spiral. The ovary and vitellarium, being nearer the 

 ventral surface, appear between the furrows d' and e, while 

 the ducts lying nearer the dorsal sur- 

 face bend posteriorly, and their ter- 

 minal portions appear posterior to 

 the furrow e on the dorsal surface, 

 and finally reach the surface almost 

 midway between the dorsal furrows 

 bounding b. At first glance it ap- 

 pears that if the position of the genital organs is correlated 

 with the form of the proglottid, the duct should open some- 

 where in the region c instead of passing posteriorly under the 

 dorsal furrow c, as it does. As a matter of fact, however, its 

 position is the only one possible in the spiral proglottid b. 

 Since the spiral segment b lies somewhat obliquely, i.e., with 

 its ventral surface somewhat anterior to the dorsal, the position 

 of the organs at b' between the dorsal furrow e and the ventral 

 d' is only apparent. In reality they are in about the normal 

 position in their segment b. The outer end of the ducts is 

 rudimentary, consisting of a scarcely visible strand of cells, 

 and there is no enlargement in the region of the pore. More- 

 over, the inner end of the vas deferens instead of running 

 anteriorly to the ovary and vitellarium, as is usual, is posterior 

 to them, as seen in the figure (b'). This position of the inner 

 end of the vas deferens posterior to the ovary is peculiar and 

 is probably due to the oblique position of the segment b. 



