48 
H. E. Jordan 
enter into the formation of the middle-piece, or what is the ultimate 
fate or function of all of the earlier formed cliromidia, I am unable to 
elucidate. Morphologically the cliromidia of the three stages mentioned 
are apparently identical. In corrosive-acetic fixed material the chromidia 
appear, but are less well markcd. 
It must be admitted that direct evidence for the nuclear origin of 
chondriosomes (mitochondria) here is meägre. What may be stated 
with absolute certainty, however, is that chromidia fhst appear in typical 
form in files and clumps external and closely applied to the nuclear wall 
(figs. 23 to 27). The apparently direct evidence for a passage from the 
nucleus is rendered uncertain bv reason of the facts; 1. that only a re- 
latively small number of cells (possibly abnormal, though with no other 
marks of abnormaüty) show a passage of granules from nucleus to cyto- 
plasm — but it may possibly be due to a process of very brief duration; 
2. the difficulty of differentiating between possible products of nuclear 
extrusion (e. g. basichromatin granules) and true chondriosomes; 3. some- 
what greater irregularity of form and size of the original chromidia than 
the mitochondria of later stages; 4) karyosomes and net-knots of nucleus 
may resemble chondriosomes of cytoplasm, thus giving the misleading 
impression of nuclear origin. 
The fact that mitochondria do not typically appear in nuclei (e. g. 
Blatta, Cavia, Triton , etc., Duesberg 1910) when stained with specific 
mitochondrial stains (Bexda’s stain) does not necessarily argue against 
a nuclear origin. The nuclear forerunners of cytoplasmic chondriosomes 
may not have reached a stage of Chemical elaboration susceptible to some 
mitochondrial stains. A parallel of such a condition is that described 
by Meirowsky (1908) for the melanic granules of pigmented epidermis 
where the nuclear forerunners are colorless. While the question of origin 
of the mitochondria in this material cannot be absolutely definitely settled, 
I believe that the almost final evidence of a transit of granules from 
nucleoplasm to cytoplasm. coupled with the fact that the appearance of 
the mitochondria in the cytoplasm is coincident with a transient loss of 
staining capacity of the nuclear reticulum, argues cogently for a nuclear 
origin of chromidia (and mitochondria). It is just possible, moreover, 
that we are here actuallv dealing with two different elements : chromidia 
and mitochondria, one nuclear in origin, the other cytoplasmic. However, 
if the two are identical, or different stages in the elaboration of the same 
substance, as held by some cytologists (e. g. Heidenhain) the nuclear 
origin of chondriosomes is practically established. This point will be 
further discussed in section X, C. 
