MITOCHONDRIA IN TISSUE CULTURES 357 



only as very thin threads, but that at forty-eight hours the 

 threads are thicker and also some granules are present. These 

 mitochondria have heavy stained edges with a clear mark 

 substance. 



Duesberg ('08) finds the same for the chick, but in the rabbit 

 he describes the mitochondria in the early fertihzed egg as small 

 granules, which increase in volume and become large granules 

 at the end of the third day. The large granules have a clear 

 central part and dark outer edge. They flow together and build 

 rods and threads. Rubaschkin ('11) finds only granules in the 

 early guinea-pig development. He claims that the granular 

 form of mitochondria is the most pi;imitive and indifferent form. 



So far as could be observed, there is no special difference in 

 the shape of the mitochondria present in the cells of the growth 

 from a piece of a three-day chick embryo from that present in 

 the growth from a piece of ten-day chick embryo. Only those 

 cells show exclusively the small granules, which contain many 

 fat globules or vacuoles. We have observed the cells of a 51 

 hours growth which contained only the granular type of mito- 

 chondria to contain at 70 hours mostly thread types (fig. 9 a-f ) . 

 The threads were formed by the stretching out of the granules 

 rather than by fusion of granules although such fusion of granules 

 does take place. When a preparation is studied from day to 

 day it is clear that the shape of the mitochondria changes and 

 that no one shape is constant for any one age. 



Brown ('13) finds that in the male germ cells of Notonerta 

 the mitochondrial fibers and threads arise in part at least from 

 spherical-shaped mitochondria. 



Schaxel ('11) claims that the shape of the mitochondria varies 

 with the method of fixing and staining inasmuch as by the 

 Benda treatment the rod-like forms predominate while after 

 the Altman treatment the granular type predominates. While 

 there have been few observations made as to the effect of various 

 technical methods upon the shape of the mitochondria they 

 appear to be such malleable structures that it is quite probable 

 that their shape could be altered by different methods. 



