1 68 C M. CHILD. 



The preceding figures are sufficient to indicate the general type 

 of development of the genital ducts as regards division. Since 

 we are concerned with the cytology rather than with the mor- 

 phology, it is unnecessary to follow the development of the struc- 

 tures step by step, for the later stages show nothing of impor- 

 tance cytologically, which cannot be observed in the earlier 

 stages. Amitosis continues to be the characteristic method of 

 nuclear division throughout the development. 



2. Other Proglottidal Structures. 



The remaining figures (Figs. 7-19) are selected as examples 

 from a large number of camera drawings of parenchymal 

 structures. 



Fig. 7 (PL IX.) probably represents one of the smaller nephridial 

 ducts at an early stage in transverse section. One very clear 

 case of amitosis and two other probable cases are visible. 



Fig. 8 (PL IX.) and Fig. 9 (PL X.) are taken from the region 

 of the lateral longitudinal nerve-cords in the growing region just 

 posterior to the scolex. In this part of the body the cytoplasmic 

 areas about the nuclei are more extensive than further posteriorly. 



Figs. 10—14 (PI- X.) show cells and syncytial masses from the 

 general parenchyma in the region where the proglottidal bound- 

 aries are just becoming visible, i. e., in a region of rapid prolifera- 

 tion of the parenchymal nuclei. Not a single case of mitosis has 

 ever been observed in this region. 



Two cells from the interproglottidal glands are shown in Figs. 

 15 and 16 (PL X.) at a stage where differentiation is advanced. 

 In early stages the regions where these glands appear are not 

 visibly different from other regions. The first visible indication 

 of gland-development is the formation by amitotic proliferation 

 of groups of nuclei along the interproglottidal boundary. Each 

 of these groups gives rise to a considerable number of elongated 

 unicellular glands like those in the figures, arranged radially 

 about a common outlet. Amitosis is much more frequent before 

 differentiation occurs, but as Figs. 15 and 16 indicate, often 

 occurs after differentiation is somewhat advanced. The figures 

 show the earliest visible stages in the formation of the secretory 

 product. The cytoplasm gradually becomes filled with deeply 

 staining, granular masses. 



