Limits oF DivistBitity or Living Matrer- 331 
determining the limits of divisibility of living matter, it is of 
importance to decide whether such a pluteus arises from a 
piece of an egg the mass of which amounts also to one- 
eighth of that of the total egg. We must therefore know 
whether the embryos originating from fragments of an egg 
grow more rapidly or more slowly than those which arise 
from an entire egg. Now, as I have mentioned before, it is 
a general rule that the smallest pieces after having attained 
the blastula stage develop less rapidly than those which are 
formed from an entire egg. In my earlier experiments on 
growth and regeneration in Tubularia I found that develop- 
ment and growth are functions of the same variables; there 
can be no doubt that to a certain extent development is only 
a function of growth. It is therefore probable that the 
embryo arising from a small fragment of an egg grows less 
rapidly than that arising from an entireegg. Itis therefore 
also probable that a pluteus the mass of which amounts to 
only one-eighth of that of a normal pluteus has developed 
from a fragment of an egg which contained more than one- 
eighth of the substance of the entire egg. I will, however, 
not deny the possibility that a later observer may perhaps 
find a still smaller pluteus, even though the large number of 
my experiments renders this scarcely probable.’ But I 
believe that even in such a case the limit which I have given 
will suffer no great reduction. The divisibility of the egg is 
therefore very limited, if one demands that the fragment 
shall develop into a pluteus. 
6. So far as my present experiments are concerned, I am 
not yet able to say where the limits of divisibility lie, when 
it is only required that the piece develop into a blastula. 
The tiniest pieces of isolated egg-protoplasm still divided if 
1 Boveri has since stated that he found a plutcus whose linear dimensions were 
only one-third of those of a normal pluteus of the same culture. But asa slight 
retardation inthe growth of the arms may easily lead to such a result, I think that, 
on the whole, the limits observed by me in many experiments will be nearer the truth 
than the one exceptional observation made by Boveri. [1903] 
Digitized by Microsoft® 
