. 
( 137 ) 
VII.—Nuclear Osmosis as a Factor in Mitosis. By A. Anstruther Lawson, Ph.D., 
D.Se., F.LS., F.R.S.E., Lecturer in Botany, University of Glasgow. (With 
Four Plates.) 
(Read June 19, 1911. MS. received July 25,1911. Issued separately November 7, 1911.) 
The recent important work of Farmer and Diepy (1910) on the cytology of certain 
varietal and hybrid ferns has raised again the interesting and absorbing question of 
the mechanism of mitosis. ‘This paper constitutes a valuable addition to the literature* 
which has bulked so largely during the last few years, and which has been instrumental 
in establishing many interesting and important facts regarding the greatest of all 
cytological problems—namely, nuclear division. The interest of this later contribution 
lies, not so much in the actual observations which these writers have jointly recorded 
—although the facts revealed are important in that they confirm the work of other 
writers and extend the range of observation,—but rather in the theory which they 
have deduced from their results and which they have put forward to account for the 
factors at work in the living cell,—factors which they believe to be concerned in the 
formation of the achromatic spindle. 
The observations made in this more recent paper confirm the generally accepted 
view that the achromatic spindle is formed from a differentiation of the cytoplasm— 
a differentiation which, on account of the active réle it is believed to play in mitosis, 
has been called kinoplasm by Straspurcer. They also confirm the view that—with 
the exception of some unessential variations in the distribution and orientation of the 
kinoplasm in the prophase—the process of spindle development is fairly uniform 
throughout the vascular plants. ‘The establishment of such uniformity is valuable, 
because it follows that the factors concerned in the process would also be uniform, and 
any theory accounting for such factors would necessarily be far-reaching in its application. 
From the facts and views expressed in the above literature we may briefly 
summarise the mitotic process as follows:—It seems that with the change of the 
spireme into definite bivalent chromosomes, the cytoplasm in the immediate vicinity 
of the nuclear membrane becomes differentiated into a series of delicate fibrils (kino- 
plasm), forming a weft which more or less completely surrounds the nucleus. In 
somatic cells this weft becomes raised up from the nuclear membrane at opposite 
points in such a fashion as to form conical-shaped caps of kinoplasm, which, on account 
of their position, are known as polar caps. The fibrils composing the caps converge at 
* STRASBURGER (1882, 1895, 1905, 1907); Brnasmrr (1894); Farmer (1893, 1895, 1905, 1910) ; OsrrrHouT 
(1897) ; Junn (1897) : SaRaant (1897); Lawson (1898, 1900, 1903); DessKr (1897); WinLtaMs (1899); Byxprr (1900) ; 
Smrrx (1900) ; Nimuc (1899) ; Morrrmr (1897, 1898, 1907) ; Miyake (1905); ALLEN (1903, 1905); OvERron (1905, 
1909) ; Bureaus (1904, 1905) ; Gr&corRE (1903) ; Davis (1899, 1909). 
TRANS. ROY. SOC. EDIN., VOL. XLVIII. PART I. (NO. 7). 22 
