266 CHILD. [VOL. I. 



The rudimentary character of the terminal portion of the 

 ducts is apparently due to the fact that the proglottid b is not 

 wholly distinct from a in this region. The posterior dorsal 

 furrow is interrupted at d" . The short portion extending to 

 the left edge is not a furrow of normal depth but a scarcely 

 visible fold upon the surface, and the left end of the main fur- 

 row at d" is also very shallow. On the ventral side there is 

 no furrow corresponding exactly to the furrow d'd", for d 1 is 

 a spiral continuation of it. Therefore the only evidences of 

 separation between a and b in this region are the slight fur- 

 rows at d" . Since the degree of separation is so slight, the 

 tendency to form a second genital pore and the terminal region 

 of the ducts is probably very slight also, but is still present, 

 as is evident from the figure. The testes are just beginning to 

 appear (not represented in the figure), and their distribution 

 corresponds exactly with the conditions on the dorsal surface. 



Figure 29. 



At the stage shown here the proliferating groups of cells 

 forming the reproductive organs are visible, and the inter- 

 proglottidal glands are more numerous. The variation is a 

 spiral, the furrow making two complete turns. The posterior 



end of the spiral furrow appears between 

 a and b at e. Upon the lower surface 

 it is a complete furrow and is continu- 

 ous with the furrow upon the upper 

 surface between b and d. This bends 

 anteriorly at the left instead of com- 

 pleting the furrow between b and a, and 



FIG. 29. 



so separates b and c at the left edge, 



continuing over the lower surface as a complete furrow and 

 passing once more to the upper surface between d and c at 

 the right and finally ending free at /. The only portion of 

 this continuous furrow which differs greatly in position from 

 the normal is the part between b and d at the left on the upper 

 surface, where it bends anteriorly and so fails to complete the 

 separation between a and b. The spiral is the result of this bend 



