Andrews . — The Effect of Gases on Nuclear Division . 527 
longer for the nucleus to finish division than was required by the control 
specimens. 
In a third series of experiments with carbon dioxide, a cell of Tra- 
descantia was left in the gas for fourteen hours. At the expiration of this 
time, as would be expected, the cell was dead. This disproves the state- 
ment of Lopriore 1 , who states that carbon dioxide may act for days 
(together) before causing a permanent cessation of protoplasmic movement. 
His error was evidently due to the use of impure carbon dioxide. 
III. Effects of a Vacuum on Nuclear Division. 
As stated, a very small quantity of oxygen is sufficient to allow 
nuclear division. By using a vacuum pump a pressure of 3 mm. of mercury 
was reached and maintained. Even at this slight pressure, resting nuclei, 
as well as those farther advanced, completed division and formed a cell- 
wall. The movement of the protoplasm does not cease even at this low 
pressure, showing the incorrectness of Demoor’s statement, that it stops at 
a pressure of 6 to 12 cm. of mercury. Whenever, for whatever reason, the 
activity of the protoplasm is made impossible, that of the nucleus is also 
suppressed. 
IV. Effects of Ethyl Ether. 
In the experiments with ethyl ether and chloroform the specimens 
were not put directly in the solution mentioned, but the vapour from 
these solutions was drawn over the cells, while in the sugar solution, 
by means of an aspirator. 
In the vapour of a 1 per cent, or stronger solution of ethyl ether 
resting nuclei of Tradescantia virginica cannot begin division. Those nuclei, 
however, which had begun division, completed it or advanced towards com- 
pletion according to the concentration of the solution, as the following 
experiments will show. 
In the vapour of a 1 per cent, solution of ethyl ether the nucleus, 
when in the prophase stage, finished division about ten minutes sooner than 
the control specimen. A series of experiments were sufficient to establish 
the fact that, as in the case of the movement of the protoplasm, a slight 
acceleration in rapidity of nuclear division was produced with a 1 per cent, 
solution of ethyl ether. 
The formation of the cell-wall also commenced even before the 
chromosomes began to separate and to move to their respective poles. 
A somewhat similar cell-division has been observed by Gerassimoff 2 in 
Spirogyra under certain conditions. The resulting nuclei were normal in 
appearance. 
In a 3, 4, and 5 per cent, solution of ethyl ether the nuclei, when near 
1 Jahrb. f. wiss. Bot., 1895, Bd. 28, p. 571. 2 Pfeffer, Pflanzenphysiologie, 2. Aufl., Bd. II, p. 46 
O O 
