232 CHILD. [VOL. I. 



appear almost normally separated, and accordingly two sets of 

 organs appear. The edge, however, is undivided and shorter 

 than the combined length of the two segments at the left, and 

 only a single pore is formed, into which both sets open. This 

 case shows much the same gradation from complete division to 

 almost complete union, as is found in Fig. 11, but here the 

 gradation occurs within a much shorter distance, for the furrows 

 are nearly complete, while in Fig. 1 1 they extend only halfway 

 across the body. 



Figure 16. 



The figure represents a peculiar case of partial division seen 

 from the dorsal side. The t\vo segments are completely sepa- 

 rated at the left by partial furrows which extend to the middle 

 on each surface. Corresponding to this separation we find two" 



complete sets of 

 genital organs. On 

 the right the two 

 portions are sepa- 

 rated dorsally b/ a 

 very shallow furrow 

 which is interrupted 



FIG. 16. 



at several points. 



This furrow passes the right edge and extends for a very short 

 distance on the ventral surface, leaving all the rest of the right 

 half of the ventral surface undivided. Corresponding to this 

 incomplete separation we find abnormalities in the genital organs. 

 There is one complete set of organs (a'} in the posterior segment, 

 and portions of a second set (b'} in the anterior segment. 



The ovary, vitellarium, and inner end of the vas deferens of a' 

 lie nearly in the middle of the undivided ventral side, almost 

 directly beneath the shallow interrupted furrow on the dorsal 

 surface, thus indicating that their position is more directly 

 affected by the conditions of the surface to which they are 

 nearest, vis., the ventral. The pore and atrium, on the other 

 hand, appear on the edge of a, nearer the anterior than the 

 posterior end. The partial furrow on the dorsal surface and the 

 right edge is very slight, i.e., the two partial segments, though 



