CHROMOSOMES 253 
nuclear division, giving rise to the nuclear reticulum 
in the daughter nucleus, are repeated in the reverse 
order at the outset of the next division; the same 
processes are withdrawn into the same chromosomes, 
and these shorten into structures identical with those 
which passed into the nucleus at its first formation, 
except that they have increased in bulk during the 
interval. 
Boveri, in fact, concludes that the separate chromo- 
somes are to be looked upon as distinct individuals— 
almost as separate simple organisms—which preserve 
their individuality throughout the history of the cell, 
and reproduce themselves, just as cells and nuclei do, 
by a process of bipartition. As far as the chromo- 
somes themselves are concerned, their typical or 
resting form is that of the short simple rods seen in 
mitosis. The branched anastomozing character seen 
during the stage of the nuclear reticulum is associated 
with the active co-operation of the chromosomes in the 
physiological processes going forward within the 
nucleus. For this reason the term ‘resting stage’ 
applied to this condition of the nucleus is a particularly 
inappropriate one. 
Boveri illustrates the amount of credence which he 
would attach to this theory of the individual persis- 
tence of the chromosomes throughout the resting 
condition of the nucleus, by means of the following 
analogy : ‘ We make water from oxygen and hydrogen, 
and from this water we can obtain oxygen and hydrogen 
again in the same proportions. Just in the same way 
as the chemist on the evidence of these facts regards 
