LFV^ER CELLS FROM CHICK EMBRYO 287 



even in all the cells of a culture, were sometimes much alike in 

 size and form (figs. 22, 24). 



No correlation between size, shape or number of mitochondria 

 and any other factor was found. All variations occurred in 

 cultures of all ages, from embryos of all stages of incubation. 

 Cells lying side by side and having, as far as possible, the same 

 history and the same environment sometimes showed wide 

 differences in character and amount of mitochondrial content 

 (figs. 6, 8). 



Some of the mitochondria seemed to be quite fluid, as they 

 bulged first in one place and then in another. The longer ones 

 alternately bent and straightened and all moved about to a 

 considerable extent. In many cells, especially flattened ones, 

 individual mitochondria could be followed for some time and their 

 successive changes in form and position observed. When vacu- 

 oles developed the mitochondria lay in strands of cytoplasm 

 around them (figs. 22, 25). As the cells degenerated and died 

 the mitochondria lost their clear-cut outlines, becoming swollen, 

 shadowy, indistinct bodies of irregular spherical form, filling the 

 whole cell and giving it the appearance of a mass of grayish 

 granules (figs. 18c, d, e). If they had been previously stained 

 with janus green they lost their color during this process. 



The living mitochondria stained a uniform, deep greenish-blue 

 with janus green; they did not stain satisfactorily with janus 

 black no. 2. Only two fixatives — Zenker without acetic acid and 

 osmic acid vapor — gave entirely satisfactory results for the 

 mitochondria. The stains which gave good results after Zenker, 

 were haematoxylin and hemateine alone, hemateine and carmine, 

 and Bensley's stain (figs. 21, 22). After osmic acid vapor, 

 safranin, licht griin and hemateine gave excellent results (fig. 24) . 

 The successfully fixed and stained preparations include cultures 

 from twenty hours to eight days old, from embryos of six to ten 

 days' incubation. 



The picture presented by the fixed preparations (figs. 21, 22, 

 24, 25) is quite similar in all essentials to that of the living cell, 

 unstained or stained with janus green. The cytoplasm of the 

 fixed compressed cell is packed full of mitochondria, their out- 



