290 RUTH STOCKING LYNCH 



When neutral red was added to the culture medium these 

 bodies took it up at once, becoming a bright yellow-red within a 

 few seconds after the addition of the dye. If the solution 

 of neutral red was very weak their progressive staining could 

 be w^atched. Other granules not visible in the unstained 

 cell also appeared at the same time as yellow-red bodies in the 

 ectoplasm or in the endoplasm among the unstained mitochon- 

 dria. Before the dye was added it was not possible to distinguish 

 all the granules scattered among the mitochondria nor to see 

 nearly so many granules in the ectoplasm or intermediate region. 

 It is believed, however, that neutral red is only taken up by 

 pre-existing granules and that, although some of them were not 

 seen because of their unfavorable position, all of the granules 

 were present before the neutral red was added. Those which 

 appeared after the addition of the neutral red had the same 

 characteristics of size, shape, and behavior as the granules which 

 were visible before staining. Their staining reaction was identi- 

 cal and they had much the same distribution. Moreover, they 

 increased in size and number with the aging of the culture, as was 

 the case with the unstained granules. 



When neutral red was added to the culture medium at the 

 time the culture was made, the first cells to project from the 

 explant did not contain any unstained granules but they almost 

 always contained a few small yellow-red granules. These showed 

 the same characteristics of shape, size, distribution, and be- 

 havior as the unstained granules in ordinary cultures and the 

 granules in the cells stained supra- vitally with neutral red. As 

 the neutral red cultures aged the granules increased in both size 

 and number until in some cultures several days old they nearly 

 filled the cell and completely hid the mitochondria, giving the 

 same picture as the older cultures stained supra-vitally with 

 neutral red. This correlation between the age of culture and the 

 size and number of granules could be best worked out in those 

 cultures grown in media with the dye, as the same culture could 

 be noted at different stages, whereas in supra-vital staining 

 comparisons are dependent upon different cultures at different 

 ages, individual differences affecting the results to some extent. 



