No. 6.] THE CESTODE MO \IEZI A EXPANSA. 271 



face to form the anterior boundary of a, then making one more 

 complete turn and ending on the upper surface, thus leaving b 

 and c incompletely separated at the right of the dorsal surface. 

 The development of the genital organs is sufficiently advanced 

 in this case to show the very intimate relation of these organs 

 as regards position with the form and relations of the proglot- 

 tids. The segment a possesses its own genital mass (a 1 ), which 

 is entirely separated from all the others. This is, however, of 

 less than the normal size and does not reach the edge of the 

 segment. It is divided into two parts in its inner portion, but 

 the group of cells which would later form the ovary and vitel- 

 larium does not appear. In fact, the mass seems to consist 

 largely, if not wholly, of portions of the two ducts. It will be 

 remembered that the ducts lie farther dorsally than do the 

 ovary and vitellarium. The figure 

 is drawn with the dorsal surface 

 uppermost, and it is only dorsally 

 that the region a appears as a 

 distinct partial proglottid. On the 

 ventral surface the relations of the 

 furrows are entirely different. It 

 appears then that the dorsal re- 

 gion of a possesses a degree of individuality sufficient to cause 

 the appearance of the organs proper to this region. The ven- 

 tral region not being separated from b, the organs of the ventral 

 side do not appear. Whether the organs would in later stages 

 approach or reach the normal development it is impossible to 

 state with certainty, but the evidence seems to be against such 

 a view, for in all cases of similar abnormalities in much later 

 stages the genital organs or parts, however rudimentary they 

 may be, show the same degree of differentiation as those of 

 normal segments. 



In the large, incompletely separated segments b and c, there 

 appears another example of the close relation between the indi- 

 viduality of the segment and the presence and arrangement of 

 the reproductive organs. At the left appear normal sets of 

 organs in normal position.' At the right, however, where the 

 furrow on the dorsal surface is incomplete and that upon the 



