MITOCHONDKIA IN TISSUE CULTURES 395 



out and become scattered through the cytoplasm, or those scat- 

 tered throughout the cytoplasm may become located around the 

 nucleus. During mitosis the mitochondria become more evenly 

 scattered throughout the cytoplasm, except in the spindle area, 

 where they are usually absent. 



5. Any and every shape granule from a minute to a large 

 granule, from small short rods to long threads, loops, rings and 

 networks of various shapes and sizes can be found. Any one 

 type of mitochondria such as a granule, rod or thread may at 

 times change into aay other type or may fuse with another 

 mitochondrium, or it may divide into one or several mitochon- 

 dria. Every type of mitochondria is continually changing 

 shape and may assume as many as fifteen or twenty shapes in 

 ten minutes. The shape of all the mitochondria in a cell can 

 be changed by experimental means such as heat or hyper- or 

 hypotonic solutions. 



6. The mitochondria vary greatly in size from minute granules 

 to irregularly shaped, large granules, from short rods to long 

 threads. The size of a single mitochondrium may change by 

 the fusion of two or more granules or by the division of a single 

 mitochondrium. They also appear to increase or decrease without 

 such fusion or division. 



7. The number of mitochondria in a single cell varies from two 

 or three to over two hundred. The number of mitochondria 

 is not constant for any one kind of cell or for any phase of any 

 one kind of cell. Daughter cells contain about one-half the 

 number of mitochondria present in the mother cell. The number 

 of mitochondria increases from the daughter cell to the mature 

 dividing cell, and apparently also at times during mitosis. 



8. The quantity of mitochondria is not constant for any one 

 kind of cell. Some cells with many small granular mitochondria 

 contain less mitochondrial substance than other cells with a few 

 large granules. 



9. Degenerating mitochondria become first a series of gran- 

 ules; later the granules become vesicles and then separate into a 

 number of small finely granular rings which stain like the cyto- 

 plasm rather than like mitochondria. 



