272 CHILD. [VOL. I. 



ventral surface bends posteriorly, two sets of organs (b' and c'} 

 appear whose ducts open into a common genital pore. Each of 

 the sets is apparently complete, possessing the groups of cells 

 which will form ovary and vitellarium, as well as the vas def- 

 erens. The inner portions of these two sets are situated much 

 as they would be if b and c were normally separated from each 

 other, i.e., their position is nearly normal. The partial furrow 

 on the dorsal surface, however, does not extend to the right 

 edge of the body, but ends free before reaching it, so that 

 b and c are united here, and correspondingly only one genital 

 pore appears at d, and into this both sets of ducts open. But 

 the question now arises as to the reason for the connection of 

 the organs b' with this pore. Normally these organs would 

 open on the edge at some point not far from/", but, owing to 

 the arrangement of the proglottids in this case,/ is the point 

 of intersection of the furrows, i.e., does not possess the fea- 

 tures of the region where the genital pore normally appears, 

 for this is upon the edge, about midway between two furrows. 

 The only possible conclusion from the facts is that the direc- 

 tion of the ducts and their final connection with the pore are 

 correlated with the form of the proglottids in this region and 

 especially upon the dorsal side. This conclusion is confirmed 

 by the fact that the ducts cross almost at right angles a furrow 

 on the ventral side, thus rendering it evident that their arrange- 

 ment is not affected by its presence. In short, ovaries and 

 vitellaria arise separately in b' and c' , because the relations of 

 the ventral sides of the segments in that region are practically 

 those which exist in two separate proglottids, and upon the 

 dorsal surface the same is true in the immediate region of the 

 inner portions of the organs. Nearer the edge, however, 

 the relations on the dorsal side are those of a single segment, 

 so that the two sets of organs approach each other and finally 

 open in a common pore, which occupies a normal position with 

 respect to the boundaries of the proglottid in its immediate 

 vicinity. 



