1gtt] CURRENT LITERATURE 319 
usual combination in one-fourth of the F, offspring, leads the author to the 
conclusion that the difference between the wild oats and these various culti- 
vated varieties is due to the presence in the latter of an inhibiting factor which 
prevents the development of the wild characters. As he has never found 
among the numerous crosses he has made between different cultivated varieties 
any instance in which the atavists made up one-sixteenth of the F., as they 
should do if different varieties possessed different inhibiting factors, he con- 
cludes that the same inhibiting factor is present in all the cultivated varieties, 
and that the different degrees of development of the awns and hairiness of 
the glumes which have been found to be dependent upon independent genes, 
must remain latent in the wild oats until the origin of an inhibiting factor 
brings them to light. On this ground he argues that the degree of discon- 
tinuity which results from any mutation depends upon the number of latent 
genes which are brought into manifestation by it, and also that various appar- 
ent correlations may result from the disappearance of a factor which had 
simultaneously inhibited both of the characters which appear to be correlated. 
The author does not take into account the hypothesis of “variable potency,” 
which could also be made to explain how the same inhibiting factor in the 
various cultivated varieties could produce such various degrees of develop- 
ment of awns, hairiness of the glumes, etc., as are displayed by them.— 
GrorcE H. SHULL 
Mitosis in Spinacia.—This extensive investigation by Sromps,® written 
in Dutch, but with an eleven page résumé in German, deals with mitosis in 
both vegetative cells and in the microspore and megaspore mother cells. 
€ 2x generation shows 12 chromosomes arranged in pairs, which can be 
distinguished not only in the nuclear plate but also in the prophase, and pairs 
probably persist in the resting nucleus. No continuous spirem is formed, the 
two components of each pair, as soon as they can be distinguished, having 
- two free ends. A imaindioal splitting of the chromosome occurs in early 
prophase, a longitudinal row of vacuoles appearing, and these, by increasing 
in size, split the chromosome. This mode of splitting results in threads with 
alternating thickened and slender portions, but Sromps does not regard the 
thickened portions as chromomeres or ids, nor does he regard the slender por- 
tions as linin, but both are the same in substance 
In the prophase of the reduction division, before synapsis, the 12 chro- 
mosomes fuse in pairs, forming 6, each with two free ends. There is not only 
a pairing, but also a genuine fusion of the two chromosomes of each pair. No 
continuous single or double thread is formed. As the nucleus comes out of 
Synapsis, one sees 6 chromosomes, each evidently double, and the two mem- 
en 
°Stompes, THEO. J., Kerndeeling en Synapsis bij Spinacia oleracea. 8vo. pp. 
162. pls. 2. t910. A briefer account in German, which is partly a summary and 
partly a translation of the original, is published in Biol. Centralbl. 31: 257-320. pls. 
Y Sunde Igit 
