A STUDY IN CHROMOSOME REDUCTION. 605 
I have met with some evidence that a very slight diminution in the chromatin volume 
may occur, but | interpret this in the same way that Davis (1911) has recently done ; 
z.é. it is entirely due to the shortening and thickening of the threads. But this diminu- 
tion, which is a very slight one, I do not interpret in any sense as a “synaptic contrac- 
tion” as generally understood by many writers (FaRMER, 1905; GREGOIRE, 1910; 
Overton, 1909; Dicpy, 1910; and others), nor do I believe it to be a feature peculiar 
to meiosis. It occurs in all somatic divisions, for there is here also a shortening 
and thickening of the threads in the development of the somatic spiremes from the 
reticulum threads. 
So that if we accept the interpretation of this so-called contraction, in so far as it 
exists, as expressed by Davis (1911)—and for my part I believe it is the correct one, 
namely, that it is due entirely to the shortening and thickening of the threads— 
we have here a feature which is common to both somatic and meiotic mitosis, 
and therefore can have no real significance in meiotic phenomena. It should no 
longer be considered as a feature peculiar to chromosome reduction. I may add that I 
am quite in agreement with this interpretation, and feel convinced that it will eventually 
find general acceptance. 
In their recent criticisms of my paper (Lawson, 19114) both Davis (1911) and 
FarMER (1912) appear to assume that the real point of contention is one of diminution 
in the space occupied by the chromatin, when, as a matter of fact, this is of secondary 
importance. The real point of contention is whether or not there is any fusion, or 
intimate association of chromatin filaments during the period known as synapsis, and 
of what significance such a union bears to the real act of chromosome reduction. I 
have attempted to make it clear, therefore, that the only question of importance in this 
connection is not whether the shortening and thickening of the threads bring about 
a slight diminution in the chromatin volume—for it is generally agreed that the spireme 
threads do shorten and thicken,—but whether or not there is a co-mingling and fusion 
of the threads at this time. I have examined a great many preparations showing this 
phase of the nucleus, and it seems to me a matter of no significance whatever if the 
shorter and thicker spireme threads of the early spireme stage seem to fill a volume 
shghtly under that occupied by the same threads in an earlier and more finely divided 
as well as the figures of my paper, quite a different view of the case will present itself; for the following description 
of fig. 13 will be found on page 597: “As stated above, certain sections were passed over, because they were not 
cut in a median plane through the chromatin mass, In this connection it might be well to point out that when the 
nucleus reaches its full size, it may be 25u or 30u in its longest diameter ; and cutting sections of an anther at this 
time, we invariably obtain numbers of sections of cells that do not pass through the median line of the nucleus. 
Some of these sections may show a very large nuclear cavity and a very small shaving of chromatin at one end. 
Such small areas of chromatin at first suggest a considerable contraction, and they were frequently found. This 
fact is mentioned here because I feel sure that some of the figures that have been published to show the synaptic 
contraction have been drawn from such oblique sections. Fig. 13 is inserted here to illustrate this point. It was 
drawn from a section that was not median.” 
Ihave made these quotations at length, because I believe this inadvertent overlook on the part of Professor FARMER 
will be very misleading to those who have not read the text of my paper carefully ; while the paragraph itself is a 
complete reply to the criticism. ~ 
