604 DR A. ANSTRUTHER LAWSON ON 
perfectly median section of an unsymmetrical mass whose irregular form extends in 
several planes. In sections of such stages the chromatin mass may appear slightly 
smaller in its sectional area, and this should not be interpreted as indicating a diminution 
in the chromatin volume. 
From the conditions shown in figs. 2, 3, and 6, it seems evident that the rate of 
increase in the amount of karyolymph within the nuclear cavity is greater than the rate 
of shortening and thickening of the chromatin threads. The one is obviously much 
more rapid than the other. This inequality of rate results in a withdrawal of the 
nuclear membrane from the chromatin mass and not a withdrawal of the chromatin 
mass from the membrane—as interpreted by many writers and recently insisted upon 
by Davis (1911). It also results in the maximum size of the nuclear vacuole having 
been reached before the spireme threads have been fully developed. As shown in figs. 
3, 6, and 7, there appears a large clear space, filled with nuclear sap, beyond the limits 
of the chromatin area. The characteristic lateral position of the chromatin mass during 
the growth period has already been explained and accounted for in a previous paper 
(Lawson, 19114), and I am still of the opinion therein expressed. 
I have elsewhere expressed the view (Lawson, 19114) that high osmotic tension 
explains the fairly sudden expansion of the nuclear cavity and is responsible for this 
meiotic growth period. Professor Farmmr (1912) has expressed the opinion that this 
view is probably correct. No opinion, however, has been expressed as to the reasons for 
this sudden change in the osmotic relations. In this connection it may perhaps prove to 
be a fact of some significance, that the accumulation of the nuclear sap is always accom- 
panied by a change in the form of the chromatin. If we compare figs. 1, 2, 3, and 6, 
it becomes perfectly evident that as the nuclear vacuole becomes larger and larger, the 
chromatin threads become more sharply defined, shorter and thicker. In other words, 
it would seem that as the chromatin substance becomes less finely divided, endosmosis 
proceeds. Although there is, as pointed out above, a difference in the rate of these 
changes, one is very much tempted to see here a correlation between the chromatin (an 
osmotically active substance), which is undergoing a change to a more condensed form, 
and the varying osmotic relations expressed in the increased amount of karyolymph. 
I am still of the opinion that no real contraction—as ordinarily understood by the 
term synapsis—occurs during the meiotic growth period. In the case under observa- 
tion there was no appreciable diminution in the cubical space through which the 
chromatin is distributed.* I do not maintain, however, that this is true for all cases. 
* Farmer (1912). In this connection Professor FARMER makes the following statement : “A critical study of his 
own figures convincingly proves that, even in the object selected by Dr Lawson himself, a contraction of the chromatin- 
containing mass clearly occurs during synapsis. This is shown by a method of tracing, and also by calculation based 
on the diameters actually figured. Thus, as nearly as could be measured, the diameters of the mass taken as a sphere, 
shown figs. 1, 7, and 13, are respectively 24, 22, and 20 mm. The volume of the respective spheres occupied by tl 
chromatin works out at 7238, 5575, and 4190 cub. mm. That is to say, a shrinkage occurs of about 43 per cent., a8 
between the presynaptic stage of fig. 1, and the synaptic stage of fig. 13.” 
To those who have not had an opportunity of reading my paper on ‘“‘ The Phase of the Nucleus known as Syna 
such a criticism will no doubt appear to be very damaging ; but to those who have made a critical study of the text 
