5i 
in the Root- Apex of Phaseolus . 
division or other active condition of the nucleus. But it is not easy 
to arrive at any definite conclusions as to their chemical relations, or as to 
the exact role of the nucleolus in the metabolism of the nucleus. The 
increase in size of the nucleolus in the resting stage probably takes place 
at the expense of materials brought into the nucleus from the cytoplasm. 
In the transformation of these materials into chromatin there are, it seems 
to me, three alternatives as to the way in which they may be dealt 
with : — 
(i) They may be taken up by the nucleolus directly from the cell-sap, 
and elaborated into chromatin, or (2) they may be first of all elaborated in 
the nuclear thread, and then passed on to be simply stored up in the 
nucleolus, or (3) they may be partly elaborated in the nuclear thread, 
and then passed on to be more completely elaborated in the nucleolus. 
Farmer’s suggestion (loc. cit, p. 512), ‘ that the nucleolus, though not in 
itself containing chromatin, is able to furnish at least one, and that prob- 
ably the albuminous constituent of this substance/ would not explain the 
presence of the phosphorus-containing substance, which both Macallum and 
I find in such abundance in many vegetable-nucleoli. 
Miss Huie 1 has made some interesting observations which bear upon 
this point and which seem to support the second, or possibly the third, 
alternative. In the gland-cells of Drosera during food-assimilation the 
nucleolus becomes smaller, whilst the chromosomes (nuclear network) 
become larger. The cytoplasm becomes impoverished and scanty in 
amount. Some time after feeding, the nucleus again becomes normal 
and the cytoplasm returns to its former condition. This indicates that 
the nucleus is the seat of metabolic activity, and that it is in the nuclear net- 
work, and not in the nucleolus, that the changes take place. But the 
diminution in size of the nucleolus, which is coincident with the increase in 
size of the nuclear network, seems to show that nucleolar substance is 
required before this metabolism can take place, or, in other words, that 
the activity of the nuclear thread is set up by the passage of nucleolar 
substance — chromatin or nuclein — into it, and that when the nucleus re- 
sumes its normal condition the nucleolus becomes restored to its original 
size by taking up the chromatin-material again from the nuclear thread 2 . 
This is in harmony with Kossel’s conclusion that the formation of new 
organic matter is dependent on the nucleus, and that nuclein (chromatin) 
plays a leading role in this process 3 . 
It appears to be always the case, that when cells are in an active 
metabolic condition, the nuclear thread becomes prominent, whilst the 
1 Changes in the Cell-organs of Drosera rotundifolia , produced by feeding with Egg-albumen, 
Q. J. Mic. Soc., New Ser., xxxix, 1897, p. 387. Further Study of Cytological Changes produced in 
Drosera, Part II, Q. J. Mic. Soc., xlii, 1899, p. 203. 
2 Cf. Farmer, Ann. Bot., ix, 1895, p. 495. 3 See Wilson, The Cell, &c., p. 340. 
