578 
C. F. U. MEEK. 
in fine tliveiids by the membrane as it contracts. When the 
kai’yolymph has completely passed into the cytoplasm the 
nuclear membrane is seen to have drawn the chromosomes 
into a compact group, and the membrane then envelops each 
chromosome, which thus receives an independent osmotic 
system. Moreover, since the contracting- membrane draws 
after it a portion of the cytoplasmic reticulum in the form of 
fibres, each chromosome at this time is furnished with 
numerous fibres attached to the membrane enveloping it ; 
and, since the fibres are said merely to represent lines of 
tension, each chromosome is compelled to assume a position 
such that its major axis is parallel to the equatorial plane. On 
arrival at the poles each daughter-chromosome becomes vacuo- 
lated by endosmosis ; and the formation of a unclear vacuole 
in each daughter-cell is regarded as an inverse repetition of 
the process seen in the prophase, in that karyolymph flows 
back from the cytoplasm through the membrane enveloping 
the chromosomes, thereby causing this membrane to expand. 
He attributed the apparent destruction of the nuclear mem- 
brane in preparations to the action of fixing reagents, which 
kill the cytoplasm; and pointed out that in the living cell we 
have no reason to suppose that it breaks down, and that, if it 
does break down, a new membrane must at once be pre- 
cipitated by the cytoplasm. Thus the achromatic figure is 
regarded as a passive result of the movements in mitosis, and 
the fibres as the expression of lines of tension. The fibres 
neither grow out and attach themselves to the chromosomes, 
nor exercise a tractive force upon the latter ; and the appa- 
rent movetnent of fibres, as seen in the convergence of cones, 
is merely an illusion produced by local alterations of tension 
entailing ti-ansference of expression from one locality to 
another. 
At this time an explanation of cell division was put forward 
by Robertson. He said that, iu the polar synthesis of nuclein 
from lecithin, cholin is formed as a bye-product; this was 
supposed to diffuse in all directions, and, reaching a maximum 
concentration at the equator, to cause decrease of surface 
