248 
H. E. Jordau 
Indeed tbis seems all tbat some cytologists (Wilson [’09] and others) 
Claim for tbis bypotbesis; i. e. tbat cbromosomes like to tbose tbat 
disappear during tbe formation of a resting nucleus reappears at tbe 
next mitosis identical in number, form, relative size and arrangement. 
Tbe important evidence furnisbed by Cumingia is negative to tbe 
bypotbesis even in tbis form, except in respect to tbe number of tbe 
cbromosomes. As tbe male and female pronuclei approacb each 
other, tbe nuclear reticulum becomes more and more cbromatic 
(Figs. 28 and 29). From tbis reticulum cbromosomes condense in tbe 
sbape of long tbreads (Fig. 30) wbich enter tbe first cleavage spindle 
as elongate variously-curved rods witb terminal swellings (Figs. 31 
and 32). Tbus tbe form and size of tbe cbromosomes wbicb emerge 
from tbe Segmentation nucleus is by no means tbe same as tbat of 
tbe cbromosomes tbat entered iuto it. Xor do tbey take on tbe 
cbaracteristic sbort rod-sbape at any pbase of tbe first cleavage 
mitosis. It is only during tbe later cleavage stages (Figs. 33 and 34) 
tbat tbey again assume tbe sbape cbaracteristic for Cumingia. 
Tbere is of course some influeuce wbicb keeps tbe specific 
number constant. But as simple masses of cbromatin, cbromosomes 
cbange tbeir form and size and entirely disappear as such during 
certain phases of cell activity. Cbromosomes are essentially and 
fundamentally something eise than mere chromatin (and linin ground 
substance) Chromatin tbey take on and give off like a garment. 
The "chromatin” both of tbe nucleolus and tbe cbromosomes may 
be of tbe nature of food material to be utilized by tbe fundamental 
elements ("centers of chromosomal activity” — B. M. Davis [’Oö], 
enzymes or bormones) tbat persist tbrough tbose stages when tbe 
morpbological entities have disappeared. Tbe argument sometimes 
advanced tbat tbe cbromosomes may simply cbange tbeir cbemical 
Constitution bas slight bearing in tbis connection, for if tbey still 
retained tbeir original form during tbe resting stage tbey ought to 
appear wben acid or neutral dyes are employed. Tbis is not tbe 
case. Tbere are stages wben tbe cbromosomes as distinet bodies 
seem to bave really disappeared and what remains is simply tbe 
possibility (whatever tbis may mean in ultimate terms) to reform tbe 
specific number of cbromosomes. Wilson (’09) belps us to picture 
tbe matter tbus: "We migbt, for instance, assume tbat tbe cbromo- 
somes are magazines of different substances (e. g. enzymes or tbe 
like) tbat differ more or less in different cbromosomes, tbat are more 
or less diffused tbrough tbe nucleus in its vegitative pbase, but are 
