ABNORMALITIES IN CESTODE MONIEZIA. 



nephridial canals. It is taken from about the same region of the 

 neck as Fig. 55, but from another individual. The plane of this 

 figure is represented approximately by the line 56 in Fig. 53. In 

 this figure the grouping of the nuclei is more distinct than in the 

 other longitudinal sections. 



o 



These figures represent sections of approximately the same 

 region as is shown in Fig. 49, /. e., a region in which the proglott- 

 ids first become recognizable. The groups of nuclei represent, 

 therefore, the early stages of what we know to be proglottids, 

 and yet the chief differences between these figures and Fig. 44 

 consist in the larger number of nuclei and a greater degree of 

 distinctness in the groups of the former figure. 



At this point the relation of the lateral groups or zones of 

 nuclei in the anterior neck region to the proglottids requires con- 

 sideration. 



As is evident from the facts stated above, the distinct proglot- 

 tid extending across the body and marked by a convex contour 

 of the surface appears first at a considerable distance behind the 

 scolex. All through the neck region, however, occur the indis- 

 tinct groups of nuclei in the lateral regions of the central paren- 

 chyma, and, when the proglottids form, their earliest stages appear 

 to arise from the groups. 



If these groups represent the earliest stages of proglottid-for- 

 mation, then the proglottid must be laid down just behind the 

 scolex and pass backward through the neck-region in conse- 

 quence of the formation of new proglottids in front of it, until 

 finally its development reaches a stage where it becomes visible 

 externally. If the groups of nuclei anterior to the regions where 

 proglottids first become recognizable as bands of nuclei extend- 

 ing over the nephridial canals toward the median plane, do not 

 correspond to proglottids, they must be due to some other fea- 

 tures in the structure of the neck. In this case, the neck consti- 

 tutes an unsegmented region, which gradually becomes marked 

 off into proglottids. 



The facts favor the second view. In the first place, the groups 

 of nuclei are just as distinct immediately behind the scolex as 

 they are further back (cf. Figs. 47 and 48), i. i\, no development 

 occurs in them except perhaps a slight increase in the number of 



