A STUDY OF PLASTIDS AND MITOCHONDRIA 
219 
the mitochondria may be studied in the living, growing condition, fixed 
while under observation and thus preserved as permanent preparations. 
Experimental methods may be employed, by which the effect of different 
stains and reagents may be observed directly. Such preparations, placed 
in the electric incubator at a temperature of 39° to 40° C, show a beginning 
of growth in from 10 to 20 hours. The new growth is attached to the cover 
glass and is several cell layers in thickness at first, thinning out to a single 
cell layer around the edges. Although conditions are necessarily somewhat 
different from those of the normal somatic environment, especially as regards 
circulation, and in the limited supply of oxygen since the cultures must be 
hermetically sealed, the processes of growth and of mitosis seem to go on as 
usual for a period of about three days. After this the process slows down, 
growth ceases, and the cells finally die. 
Mitochondria, conforming to the usual criteria, were found to be present 
in all cells studied. Osmic acid vapor proved to be the best fixative, while 
the vapors of acetic and other acids caused immediate and total disintegra- 
tion of the mitochondria. The bodies appeared as threads and granules 
of the most varied shapes and sizes, just as they have so often been described 
in fixed preparations. They are not, however, constant in form or in size 
under these conditions, but ar^e constantly changing in appearance. They 
are described as undergoing division, as fusing to form larger bodies,- and 
as disappearing and reappearing in the cells in a manner not accounted for. 
During mitosis they are distributed regularly about the cell, so that they 
are apportioned to the daughter cells in approximately equal numbers. 
No connection of the mitochondria with the production of fats, such as 
described by Dubreuil ('13), was noted in these preparations. In conclu- 
sion, the authors state: ''The mitochondria are extremely variable bodies, 
which are continually moving and changing shape in the cytoplasm. They 
appear to arise in the cytoplasm and to be used up by cellular activity. 
They are, in all probability, bodies connected with the metabolic activity 
of the cell." 
Lewis and Robertson ('16) found that the above described method of 
tissue culture was well adapted to the study of spermatogenesis in the 
grasshopper, Chorthippus curtipennis. In the young spermatid the mito- 
chondria were in the form of a granular Nebenkern. After certain internal 
changes, the import of which was not clear, the Nebenkern was seen to divide 
into half-spheres. These half-spheres then elongated to form granular sacs, 
which, as the tail grew out, formed two irregular strands. These irregular 
strands finally fused to form "two continuous threads of even width, ex- 
tending from the centrosome body, or middle piece, almost to the end of the 
tail." 
The authors conclude that "it does not seem possible that bodies which 
have to do only with the metabolic activities of the cell should underg6 such 
an exact behavior as shown, for instance, by the division of the Nebenkern 
