CHROMOSOMES AND MITOCHONDRIA | 283 
stain seems to be more selective than any other for 
mitochondria and is of great value for this reason. 
Mitochondria most often appear as_ spherical 
or elongated granules about 0.001 mm. diameter. 
These granules may become arranged in a series, 
thus forming a chain, and the granules in a chain 
may fuse into a homogeneous rod. Different forms 
are present in different kinds of cells or even in the 
same cell at various stages in its evolution or func- 
tional activity. Some investigators (Prenant, 1910) 
maintain that the homogeneous rod is the primitive 
condition and that the granules are formed by the 
disintegration of such rods; to others just the 
reverse seems to be true (Rubaschkin, 1910; Dues- 
berg, 1912). 
The chemical: constitution of the mitochondria 
has been studied by a number of investigators. 
Regaud (1908) has shown that the mitochondria of 
the ~seminal epithelium are not histochemically 
identical. He distinguishes three sorts of granules: 
(1) those which resist the action of acetic acid and 
are stainable without being previously immersed in 
a solution of potassium bichromate, (2) granules 
which resist acetic acid but require intense chromisa- 
tion, and (3) granules which do not resist acetic 
acid and demand chromisation. Fauré-Frémiet, 
Mayer, and Schiffer (1909) have studied the mito- 
chondria by microchemical and comparative methods 
and reached the conclusion that they are lecithal- 
bumins. 
Mitochondria have been noted in all stages of 
