48 EDWIN G. CONKLIN 
may be based. From the 2-cell to the 32-cell stages the growth 
in volume of the resting nuclei lies between 171 per cent for 
maximum nuclear size, and 292 per cent for mean nuclear size 
while the growth of the chromosomal plates is 248 per cent. It 
seems very probable therefore that the growth of the chromatin 
during these stages lies somewhere between 171 per cent and 292 
per cent, or an average increase for each of the 30 divisions rep- 
resented of from 5.7 per cent to 9.7 per cent. In all cases the 
growth of the chromatin falls far short of 100 per cent, or a doub- 
ling, in each division cycle. In Strongylocentrotus, Erdmann 
(08) finds that the ratio of chromatin to plasma is seven times 
greater in the pluteus than at the beginning of development, and 
she points out that this means that plasma contributes to the 
growth of the chromatin. 
While the chromatin as such is peculiar to the nucleus, there 
can be no doubt that large quantities of chromatin escape into 
the protoplasm. Such chromatin usually loses its distinctive 
staining reaction and presumably suffers chemical change. On 
the other hand we know that chromatin grows at the expense of 
substances received from the protoplasm. The work of Masing 
(10) on the nucleinic acid content of the egg indicates that this 
important constituent of chromatin is about as abundant in 
early stages as in later ones; he supposes that it exists in the pro- 
toplasm. 
d. Chromosomes. What is true of the quantitative relations 
of the chromatin as a whole is true also of the individual chromo- 
somes; those formed from large nuclei are larger than those from 
small ones; the chromosomes do not double in volume in each 
successive cleavage, but they become individually smaller as 
cleavage progresses. These facts are not difficult to demonstrate, 
but they are difficult to express in any numerical proportion, owing 
to the irregular shape and small size of the chromosomes, which 
make it very difficult to determine their volume. 
In Crepidula the chromosomes are very small and numerous, 
the full number being probably 60, and they are usually crowded 
together so that it is difficult to photograph them, or even to 
draw their outlines accurately, and since they are so small it is 
