192 CORA J. BECKWITH 



cells. In the other forms described, Schaxel emphasizes the 

 fact that that part of the extra-nuclear chromatin, not used in 

 the formation of the yolk, remains between the yolk-spheres as 

 'intra vitelline chromatin.' The latter has been traced in the 

 echinoderms and annelids to the end of cleavage, when it has 

 completely disappeared, having, presumably, been used in the 

 process of differentiation. The cells of the blastula are again in a 

 state of 'achromasie.' In Aricia, in which later stages of devel- 

 opment were studied, a 'secondary chromatin-emission' occurs in 

 the cells of the gastrula. The granules of this emission are used 

 in the differentation of cells into body tissues. In later papers^ 

 Schaxel describes mitochondria in the cell, in addition to the 

 extra-nuclear granules. He considers the two elements distinct, 

 since the mitochondria are present in the egg before the chrbmatin- 

 emission occurs and also remain as constant cell-constituents 

 from cell getieration to generation, while the protoplasmic chroma- 

 tin disappears from the cell in the process of differentation. 



Schaxel's conclusions regarding the chromatic nature of the 

 extra-nuclear granules are based on both staining reactions and 

 morphological evidence. He is well aware that not too great 

 emphasis can be placed on the fact that the granules stain as 

 chromatin, yet this fact combined with the morphological evi- 

 dence, has some weight. The morphological argument seems 

 stronger, since granules outside the nucleus at the end of threads 

 having few or no granules, strongly suggests the passage of those 

 granules through the membrane. His figures are most convincing. 



My immediate purpose has been to obtain more accurate evi- 

 dence for or against these interesting conclusions by testing the 

 staining reaction of the extra-nuclear granules in order to deter- 

 mine if possible to what extent such reactions can be relied upon 

 as an indication of their nature; but I have also endeavored to 

 study the origin and ultimate fate of the granules, their relation 

 to the yolk and mitochondria, and the origin and fate of the 



2 Mitochondria as such are not described in Schaxel's early papers. They are 

 described carefully in his later ones on echinoderms and annelids to correct the 

 mistaken conception that the nuclear granules represent the chromatic origin 

 of the mitochondria. 



