50 EDWIN G. CONKLIN 
be seen that the larger nuclei give rise to larger chromosomes than 
do the smaller ones. 
Since the probable error is much greater in the measurement of 
individual chromosomes than of whole chromosomal plates, I 
have not attempted to measure individual chromosomes in each 
stage of the cleavage; on the other hand the dimensions of the 
chromosomal plates are given in table 4 for each cell up to the 
32-cell stage. These measurements show that from the 2-cell 
to the 32-cell stage the chromosomal mass increases in volume 
248 per cent or an average of 8 per cent for each of 30 divisions. 
The chromosomal plates, and consequently the individual chro- 
mosomes, grow smaller as cleavage advances, but in the same gen- 
eration of cells small nuclei have smaller chromosomes than large 
ones. In short, the size of the chromosome is dependent upon 
the size of the nucleus from which it comes, rather than upon the 
cell generation to which it belongs. 
In the main these observations are in harmony with those of 
Erdmann, and Baltzer, to which reference has already been made. 
In Crepidula, as in the echinids studied by the authors named, the 
individual chromosomes grow smaller as the cleavage advances, 
but this is causally related to the decrease in the size of the nuclei 
and of the cells, and where, in later cleavage stages, the nuclei 
and cells remain large, there the chromosomes also are larger than 
in smaller sister cells. Just as the size of the nucleus is con- 
nected with the volume of the cytoplasm in which it lies, so the 
size of the chromosomes is connected with the volume of the 
nucleus from which they come. 
Montgomery (’10) has found that the sperm cells of Euschistus 
are of two sizes and he concludes (p. 127), that “‘it is probable that 
the large sperm possess no more chromatin than the small, 
though the heads in the former are much larger. The dimegaly 
expresses itself accordingly in differences of amount of karyolymph 
and of the substance (linin) that composes the mantle fibers, but 
much more markedly in the amount of cytoplasm.’ He finds 
also that the mitochondria (idiozome) increase directly with the 
amount of cytoplasm. According to my observations chromo- 
somes from large nuclei are larger than those from small ones of 
