ON DEVELOPMENT ETC. OF PITORONTS. '"JIS 



iiitonscly stained eliromatin pieces are in l»oth nuclei dispersed 

 witliont :iny apparent order througliont tlie finely granular nncleai- 

 substance. At one sjiot outside the male jironuclens, tlierc is 

 visil)lc a small and clear arclioplasmic (?) s]^ace surrounded l»y 

 a set of exceedinii'ly fine radial rays. The two polai- liiohulcs of 

 this eg,!;" were distinctly yisihle in other sections which haye 

 not been fii;ur(Hl. 



h. XoTES ON Segmentation. 



Our knowledge of the mode of segmentation in JVinron'is is 

 far from 1)eing satisfactory. Metscitnikoff ('82) gives no account 

 of the process. Foetttnger ('82), if one may judge from his 

 figures, seems to haye seen the egg undergoing to taland unerpial 

 segmentation. According to CALD\yELL ('82), the segmentation 

 ^'' proceecU with consiclerahle regularity " [I.e., ]>. o74) ; Roule ('90) 



says 'T ovule féconde .mhit une segmentation totale fort reguliere " 



[le., ]xll47). E. Sciiultze ('97) simply says ''Ich mh das Ki 

 sich total und unäqual furchen ' {I.e., p. 6). 



jVIy ohseryations of the process were made on eggs found in 

 the eml)ryonal mass as w^ell as on those artificially fertilized. As 

 the former showed comparatiyely rarely the earlier stages of 

 the segmentation, it was necessary to haye recourse to the latter 

 for filling uj) the gaps of ol)seryation. 



Soon after the formation of the second ])olar glohule and the 

 disappearance of the micropyle-like spot the first cleayage line 

 makes its appearance, passing on one side of the ])olar glohidcs 

 (figs. 1 and 21). At this stagx» T can not ])erceiye any ditlercnee 

 in size and structure l^etween the two hlastomeres. The second 



