PHYSICS OF SEGMENTATION. I IJ 



Lillie * in two recent papers has emphasized the importance 

 and essentiality of these electrical phenomena for segmentation, 

 but, inasmuch as he ignores to a certain extent the consideration 

 of the factors we have emphasized, and because we believe it 

 can be shown that his own view is incomplete without this, it may 

 be allowed us to quote quite extensively and in abstract. 



Lillie in his first paper finds that " the tendency of colloidal 

 particles to collect at the electrodes indicates that they carry a 

 surface charge, either positive or negative." Precipitation can 

 be caused by ions bearing charges of opposite sign to those 

 of the particles, liquefaction by those of like sign. " The 

 researches of Picton and Under, and Hardy indicate that the 

 nucleo-proteids especially the chromatin of dividing cells and of 

 spermatozoa are pronouncedly acid and therefore electronega- 

 tive ; cytoplasmic proteids are conversely basic and positive. 

 Accordingly a difference of electrical potential exists between 

 cytoplasm and chromatin in the cell, which difference is greatest 

 at the time of mitosis, when the chromatin is most strongly acid. 

 This potential difference may constitute the primary and deter- 

 mining condition of mitosis." 



In confirmation of the correctness of this view he finds that 

 "in all cases the appearance of the cytoplasmic radiations and 

 the formation of the mitotic figure are accompanied by a passage 

 of the nuclear chromatin into a phase rich in nucleic acid. 

 Evidently the two parallel series of changes are intimately con- 

 nected. Furthermore, the marked resemblance between the rays 

 of the mitotic figure and the electric and magnetic lines of force 

 are additional indications that the process is essentially electrical 

 in nature. The position of the chromosomes during mitosis in- 

 dicates a mutually repellent action similar to that of similarly 

 charged bodies. The same action takes place in the chromatin 

 filament whereby it assumes a coiled or spiral form." 



In his second paper his purpose is to show the necessity of 

 these electrical conditions for segmentation. Evidence for this is 

 that " cytoplasmic cleavage in fertilized Astcrias and Arbacia 

 eggs is prevented in solutions of non-electrolytes, although the 



1 R. S. Lillie, American Journal of Physiology, VIII., IV., Jan. I, 1903, and 

 BIOLOGICAL BULLETIN, IV., 4, March, 1903. 



