MKIHMD OF CELL DIVISION IN MONIEZIA. 29! 



first were almost entirely absent from the proglottids on which 

 most of my study of cleavage was made and that my Figs. 21-26 

 (Child, '076) are in reality sections of considerably later cleavage 

 stages than I had supposed. 



The passage of the eggs into the uterus in Mnniczia undoubtedly 

 occurs periodically and as the eggs are fertilized in the course <>f 

 ihis passage it follows that in any Dingle proglottid containing 

 ( li-avage stages not all the stages will be present. In the- pro- 

 glottids on which I based my study of cleavage it happened (hat 

 hi--i cleavages \\<-n- numerous. /. c., a period of pa -age of eggs 

 from the ovary to the uterus had occurred recently. Hut as a re- 



ex.unination ot the-e -lide- after my study of Rit h.ir.U'- material, 

 shous, tin stages bctueen the tir-t and occasional second cleav- 

 nd much later Stages were almo-t entirely absent. M\ 

 ol" supposed early ( leavages are in realitv sections ,\ t 

 containing a < < m-ii leral >Ie numl'er of nncK-i, but the plane of 

 -'' lion happen- to pass SO .1- I" show only or chielly the L 

 nuclei. Thai I could mistake ihe-e f. .r early cleavages \\a- due 

 to the tact thai I \\.t- much more interested in the condition 

 ot i he inn lei than in i he course i i leavage, and m\ observations 

 on ihi- latter poim \\tic .ml\- incidental and so led to a wrong 

 com lu-ii.n. Tim- m\ <\\v on thi- point i- explained, but I do 

 not illcr i he explanation as an excuse. 



! unhcrmoic. Richards i- ciiiiivl- ct in }\\~, a -eriion that 



liming iln- earlier cleavages tin- blastonieres possess di-tinct 

 boiimlai ii - and tl,> IS not a s\ ncytial ma--. 



< >n the other hand m\ examination of Richard-'- material 

 has enabled me to <li-co\er \\hat -eetiis to me a \ cry important 

 point that he ha- tailed to note. In his material the early 

 cleavages are, as he says, mitotic and the bla-toinerc- distinct. 

 The ( \ to] .la sin in these M. ; m- rat her dee] il\ and uniforml\- 



and i> not \acuolaled to an\ great extent. At certain Staj 

 ho\\e\er. \\hich ma\' \ar\ in ditlerent e-;^> to some extent, but 

 at \\hich tlh consists of a considerable number of blas- 



tomeres it und. a marked change in appearance. The 



cvtoplasin lose> its t ini;ibili t y to a lar^e extent and become-, 

 highly \ai-uol.ited and the di-tinct boundaries of the blastomeres 

 disappear. Apparently thoe boundaries disappear gradually, 



