IO6 CHILD. 



nuclei until the region is reached where the proglotticls become 

 distinguishable. And secondly, I have found similar groups of 

 nuclei in the neck-region of other cestodes, but in a number of 

 cases they did not correspond to proglottids, but a number of them, 

 four or five or perhaps more, were included within a single pro- 

 glottid when it formed, and a still higher number were found in 

 older proglottids. The examination of Moniezia expansa alone 

 might lead to the acceptance of the first of the two alternatives 

 stated above, for when the proglottids do appear they are 

 aggregations of nuclei in the lateral regions of the central paren- 

 chyma, of about the same size as the other groups. This com- 

 parison with other forms shows that the indistinct grouping of 

 nuclei throughout the neck region has nothing to do with the 

 formation of proglottids. The existence of t'he groups is probably 

 due to the more or less regular repetition of the dorso-ventral 

 muscles, which are most abundant in the lateral regions of the 

 central parenchyma, and perhaps also in part to the arrangement 

 of the circular muscles. Between the muscles the nuclei of the 

 undifferentiated parenchyma are aggregated into groups. Such 

 an arrangement seems to be visible in some sections, but in others 

 does not appear distinctly. 



I have considered this point rather fully because in Moniezia 

 the resemblance of the nuclear groups to the early stages of the 

 proglottids is very close. 



Returning to the consideration of the forming proglottid, we 

 find that after it becomes visible as a zone of nuclei extending 

 across the central parenchyma, a continuous increase in size in 

 all directions occurs. Some of the features connected with this 

 process of growth require attention here. 



In the early stages of the proglottid, before the furrows have 

 become visible on the surface of the body, the parenchyma-nuclei 

 are multiplying very rapidly. Fig. 5 1 shows the general ap- 

 pearance at this stage, and Fig. 57 is a section of the same 

 stage in the plane of the line 57 in Fig. 53. Here the nuclei 

 of the peripheral parenchyma are just beginning to appear in 

 groups, corresponding in position to the lateral regions of the 

 proglottids in the central parenchyma. Although in whole 

 mounts the boundaries of the proglottids are well marked, sections 



