272 Phillips on a Comparative Study of the 



loosely imbedded small granules, each of which stained deeply 

 with the ordinary (basic) nuclear stains after having been 

 properly fixed with sulphuric acid. These granules, from 

 their behavior during division and towards stains and chem- 

 ical reagents, were identical with the chromatin substance of 

 the cell nuclei of higher plants and animals, and on this 

 account were designated "chromatin granules." They had 

 no relation to the peripherally lying albuminous crystalloids 

 or to the slime vacuoles, and they never appeared isolated 

 in the peripheral protoplasm. They were therefore neither 

 identical with the slime balls of Palla nor with the "red 

 granules" of Biitschli. (17) The nuclei of the Cyanophyceas 

 differed from the nuclei of the higher organisms by their 

 lack of nucleoli and the absence of any nuclear membrane. 

 A sharp differentiation of the nucleus could be obtained by 

 fixing with sulphuric acid and staining with Heidenhein's 

 iron-alum hjematoxylin. (18) During division of the cell, 

 the small chromatin granules merged into one another and 

 formed larger masses whose chromosome nature could easily 

 be demonstrated from their behavior during division. Their 

 identity could also be traced into the daughter nuclei. ( 19) 

 As the chromosomes drew apart and took up their positions 

 at the poles of the dividing spindle, there could, in every 

 case, be made out a zone of delicate non-granular fibers 

 (striated zone) connecting the daughter nuclei. These repre- 

 sented the central fibers of the achromatic spindle of higher 

 plants. (20) The nuclear division was carried on entirely 

 independent of the cell-plate formation, and was completed, 

 or nearly so, before it had begun to grow in as a collar-like 

 ingrowth from the equator of the mother cell. The ingrow- 

 ing cell-plate slowly advanced until it forced the fibers of the 

 spindle together into a thin thread or cord which pierced the 

 cell-plate in the centre. This achromatic thread was finally 

 severed, but the cells remained connected by a pore from 

 one cell lumen to the other. (21) The polar movements of 

 the chromatin substance and the formation of a chromatic 



