68 EDWIN G. CONKLIN 
a nucleus may live for some time and show certain vital functions, 
but it is unable to grow or to regenerate lost parts. It is much 
more difficult to test the former question, for it is usually impos- 
sible to separate the nucleus completely from the cytoplasm and 
yet leave it in a medium in which growth would be possible. 
Verworn (’91) succeeded in shelling the nucleus out of Thalas- 
sicolla, but found that the isolated nucleus was unable to grow 
a new cell body; but apart from the objection that the resting 
nucleus contains a large amount of cytoplasmic substance, this 
experiment is not conclusive for it is possible that the failure to 
grow a cell body was due to the lack of a proper nutrient medium 
in which the nucleus could operate. 
The present experiment is free from most of these objections, 
though it must be confessed that one objection still remains, 
viz., it is not possible to be certain that every trace of cytoplasm 
has been removed from the yolk cell. Nevertheless the amount 
of cytoplasm left in the cell is very small and is quite indistinguish- 
able, the only visible constituents of the cell being chromosomes, 
sphere and yolk. In the growth of cytoplasm in such a cell there 
first appears a very thin layer of cytoplasm around the chromo- 
somes, then the yolk in the immediate periphery of this begins to 
dissolve and the cytoplasm increases in amount. Coincidently 
the chromosomes swell up, absorbing achromatic material from 
the cytoplasm, and in later stages the growth of both cytoplasm 
and nucleus goes forward at an increasing rate. The formation 
of cytoplasm takes place only in the presence of chromatin and 
in 1ts immediate vicinity; on the other hand the chromosomes grow 
only when surrounded by cytoplasm. This indicates that some 
influence, probably of a chemical nature, goes out from the chro- 
mosomes and leads to the solution of yolk and the formation of 
cytoplasm. Whether this influence from the chromosomes may 
act directly upon the yolk, or only indirectly through the medium 
of a minimal quantity of cytoplasm, is not certain, but it seems 
probable that the latter is the case.. After cytoplasm has been 
formed around the chromosomes, but not before, the chromosomes 
themselves begin to swell up, absorbing achromatic material 
from the cytoplasm, and the chromatin grows in quantity. Cyto- 
