622 DR A. ANSTRUTHER LAWSON ON 
With the complete diffusion of the karyolymph the nuclear membrane becomes 
closely applied to and completely envelops each bivalent chromosome. 
This change in the relative positions of the nuclear and cytoplasmic substances 
causes a tension to be set up in the cytoplasm, the latter being now obliged to occupy 
a greatly increased space. 
As the nuclear membrane recedes with the diminishing karyolymph, the cytoplasm 
immediately surrounding the nucleus becomes drawn out into a series of fine threads 
or fibrils. 
These fibrils, which later constitute the achromatic figure, thus originate directly 
from the cytoplasmic reticulum and merely represent lines of tension. 
The resolution of the multipolar figure into the bipolar arrangement is accomplished, 
not by the lateral movement and fusion of conical-shaped sheaves of fibrils, but by the 
shifting of the lines of tension as the nuclear membrane envelops each bivalent 
chromosome. 
The attachment of the fibrils to the bivalent chromosomes is brought about by the 
nuclear membrane enveloping these structures. This membrane, being a continuation 
of the same plasmatic substance as the fibrils, becomes closely applied to the surface 
of the chromosomes and thus furnishes each of these structures with a system of 
fibrils. 
The achromatic figure can thus take no active part in the separation of the 
chromosomes or in their movement towards the poles. It merely represents a state 
of tension in the cell which results from nuclear osmotic changes. 
Throughout the two meiotic divisions an exceptionally high state of nutrition 
prevails, the cells themselves being temporary storage organs. 
No resting period or reticulum stage occurs between the two meiotic divisions. 
The one mitosis follows immediately upon the other. 
This is regarded as an accelerated form of merismatic activity, and seems to be due 
to the very exceptional nutritive conditions. 
It is believed that this accelerated nuclear activity accounts for the absence of a 
reticulum stage between the two meiotic divisions. 
It is further suggested that the first meiotic division represents two ordinary 
somatic mitoses which have become telescoped into one. 
In conclusion, the writer wishes to express his indebtedness to the Executive 
Committee of the Carnegie Trust for a grant to defray the cost of the lithographic 
plates illustrating this paper. . 
