264 
George Arnold 
This serves to emphasize the fact that the chondriosome may vary 
in its composition in the cells of the same organ, of different animals. 
Thus we know that the chondriosome in the spermatocytes of the rat is 
entirely of a mitochondrial nature, whereas in the same cells of an insect, 
e. g. the honey-bee, it is composed entirely of chondriokonts. [Meves 
(1908 a); Duesberg (1910 a)]. Neither are the chondriosomes of the 
same composition in the different kinds of cells in one animal, for in the 
guinea-pig the chondriosome of the spermatocytes is entirely granulär, 
although both rods and granules occur in the cells of the pancreas. 
Hence, since the chondriosome differs in its component structure 
in different animals, it behoves us to be careful in comparing conclusions 
concerning its behaviour as described by observers who have investigated 
the same tissues, but in animals of totally different species. 
Bearing this caution in mind, we are nevertheless justified in reject- 
ing the conclusions of those authors who have derived the Nebenkern 
i. e. chondriosome, from the nucleus. For it has been clearly established 
by the work of Meves, Duesberg, Hoven, and others, that the chondrio- 
some is a purely cytoplasmic structure, possessing an identity separate 
from that of the nucleus, even in the fertilized ovum, and continuing as 
such through all the succeeding generations of cells, whether eventuallv 
it be metamorphosed or not. 
Certainly, in the case of the guinea-pig, there is not the slightest evid- 
ence in support of the derivation of the chondriosome from the nucleus 
as will be made evident in the succeeding paragraphs. 
Changes in the chondriosome leading up to the formation of the 
zymogen granules. 
The cells of the pancreas pass through three phases, which merge in- 
sensibly into each other, and which I shall call the phase of (1) secretion 
or elaboration, (2) of excretion and (3) a phase of rest. 
We should expect the first and second phases to be particularly 
marked during digestion, and the third to be most noticeable some hours 
after a meal, and when the stomaeh is empty. 
The different phases are however not synehronous for all the cells, 
so that even in the pancreas of an animal killed two hours after a plentiful 
meal (guinea-pig II), when it may safely be assumed that digestion was 
at its maximum, quite a quarter of all the cells were in the phase of rest. 
The three phases will now be described in the order indicated. 
