\<. 6.] THE CESTODE MONIEZIA EXPANSA. 269 



posterior furrow, so that the region corresponding to the ven- 

 tral side of b is cut into two parts, that nearest the edge being 

 united with c, i.e., taking b as it appears on the dorsal sur- 

 face, we find that it is not separated from c at the edge. As 

 b is bounded on the ventral surface it does not reach the edge 

 of the body at all. The position of the pore is evidently con- 

 nected with these peculiar relations. The dorsal side of /;, 

 together with c, forms a spiral. Beginning with the dorsal 

 partial furrow between b and a, the spiral furrow makes two 

 complete turns about the body. 



The rudimentary condition of the organs in b is undoubtedly 

 due to the small size of the segment. The ovary and the ovi- 

 duct are more completely developed than the vas deferens. 

 The segment b contains a number of testes and in some sper- 

 matozoa are visible. 



The position of the organs in a needs no comment. The 

 segment is of peculiar form, owing to the presence of b, but its 

 genital organs are normally situated. 



The furrows between c and d are abnormal. The dorsal 

 furrow ends at the right without reaching the edge, and the 

 ventral furrow turns posteriorly near the right edge and meets 

 the posterior boundary of c. Thus the right edge of c and d 

 is not divided by any furrow, but the dorsal furrow extends 

 almost to the edge. The ovary and vitellarium at the right of 

 c are normally placed with regard to the ventral boundaries, 

 and the ducts and pore with regard to the dorsal boundaries. 

 Both ducts cross the course of the ventral furrow at an angle 

 to reach the edge, thus indicating that relations on the ventral 

 side have little influence on their direction. At the right of d 

 a normal set of organs occurs. The figure shows, however, 

 that the two pores on the right edge of c d are near together. 

 In the region of the inner ends of the ducts the segments are 

 completely separated, and the distance between the two sets 

 of ducts is normal here. As they approach the surface, how- 

 ever, the separation between the two segments on the dorsal 

 surface becomes less and less complete, and the edge itself is 

 undivided. Thus the pores tend to form near its middle, but 

 the fact that the dorsal furrow extends so nearly to the edge 



