CELL SIZE AND NUCLEAR SIZE 47 
one to expect and this probably is due to the fact, which I (’05) 
have established in the ascidians, that the polar partsof the spindle 
are not derived from the nucleus but from the protoplasm. With 
this proviso, it is true that, within the same species, large nuclei 
give rise to larger spindles than do small ones and this may be 
held to indicate that the linin is more abundant in the former than 
in the latter. 
The fact that the spindle fibers of ascidians are composed of 
equatorial and polar parts, the former derived from the nucleus 
and the latter from the protoplasm, and the fact that these two 
portions of the spindle, and also the polar fibers, are fundamentally 
alike, indicates that the linin, like the nuclear sap, is a constit- 
uent which belongs both to the nucleus and to the protoplasm. 
e. Chromatin. The amount of chromatin undoubtedly in- 
creases during the cleavage; the resting nuclei in the later stages 
being more densely chromatic than those of the earlier stages. 
In each cell the chromatin is smallest in quantity when the daugh- 
ter chromosomes are first separated, and it grows in quantity 
during the resting period. Not all of the chromatin of the resting 
stage goes into the formation of the chromosomes of the next 
mitosis, but some of it in the form of granules (oxychromatin) 
or chromatic sap escapes into the cell body on the dissolution of 
the nuclear membrane. The larger the nucleus is and the longer 
the resting period through which it has come, the greater the 
quantity of chromatin which thus escapes at mitosis. Gardiner 
(98) estimated that the amount of chromatin which thus escaped 
into the cell body at the first maturation division of Polychaerus 
was five hundred times as great as that which went to form 
chromosomes, and conditions are similar in Styela, Crepidula, 
and many other forms. Consequently the volume of the chromo- 
somes in successive stages cannot be used as a measure of the 
growth of the chromatin. Nevertheless the growth of the chro- 
mosomal mass, as well as the growth of the entire nuclear volume, 
will give some idea as to the growth of the chromatin during cleav- 
age. Table 9, giving as it does the volumes of the nuclei and 
chromosomal plates at various stages, furnishes data upon which 
an opinion as to the growth of the chromatin of the resting stages 
