360 
The Ohio Naturalist. 
[Vol. XV, No. 1, 
five smaller, and four large, long ones, which are rather well 
individualized. The chromosomes are attached to a bipolar 
spindle and are said to undergo a transverse splitting or breaking 
at the loop end in the first division and a longitudinal separation 
occurs in the second. 
Lawson made a study of the microspores of several plants and 
arrived at a number of new conclusions in regard to the relation 
of “Osmosis as a Factor in Mitosis,” (5). He said that the 
nuclear membrane did not break down or disappear during the 
development of the spindle, but acted as any permeable mem¬ 
brane would under varying osmotic conditions. He gave drawings 
showing that when the amount of nuclear sap became very 
much reduced, the membrane drew close to each chromosome 
and finally there were as many osmotic systems as there were 
chromosomes and each chromosome has its own sphere of “kino- 
plasm. ” He holds that the achromatic spindle is simply an 
expression of the tension of the cytoplasm and is not an active 
factor in mitosis. 
In his paper, “The Phase of the Nucleus known as Synapsis, ” 
(4), he states that the condition described is not a contraction 
at all and has nothing to do with the fusion of maternal and 
paternal chromatin, so was not a critical stage in reduction. 
In his study of Smilacina he did not find protochromosomes, 
but the reticulum was found to be made up of a number of linin 
threads which approximate the diploid number of chromosomes. 
Since he found no vacuoles in the cytoplasm he concluded that 
the nuclear cavity itself was acting as a vacuole, since the spcro- 
cytes were still enlarging and also on account of the turgid appear¬ 
ance of the nucleus. By the stretching of the nuclear membrane, 
the space within was increased causing a great osmotic pressure, 
which he concluded facilitated growth. This condition is probably 
synonymous with that described by many authors as “synaptic 
contraction. ” By actual measurements he stated that he was 
able to determine that there was no contraction whatever. Thus 
the conclusion reached in the paper was, that “synapsis” is 
simply a period of growth during which the great amount of 
nuclear sap causes the nuclear membrane to distend and with¬ 
draw from the chromatin material. This was all explained as 
occurring before reduction division, because all the sporocvtes 
had merismatic activity which manifests itself in the two divisions 
immediately following. 
Sehaffner in his paper, “Synapsis and Synizesis” (14), defines 
synapsis as the formation of bivalent chromosomes from uni¬ 
valent ones by an end to end fusion and a subsequent folding. 
McClung’s term Synizesis was accepted as appropriate for the 
contractions usually observed in prepared sections showing early 
stages in reduction. Synizesis was explained as an artifact 
probably due to plasmolysis. 
