﻿BOTA.XICAL GAZETTE 



though this seems to be due partly to a misunderstanding of the term "main- 

 tenance of the individuality of chromosomes." The single spireme, which 

 results from the fusion of chromomeres upon the linin thread, enters into the 

 synaptic stage. In accord with Lawson, Miss Woolery has found by measure- 

 ments, which she records, that there is an enlargement of the nuclear cavity; 

 but, contrary to the former's conclusions, the space occupied by the chromatin 

 material is found by actual measurement, which she also records, to be less. 

 During synapsis there is a shortening and a thickening of the thread to form 

 the uniform spireme which later emerges from the synaptic ball. Unfor- 

 tunately, there are no drawings to show the thread at the time of greatest con- 

 traction. During second contraction the first appearance of the split spireme 

 is recorded, though the double structure spoken of in figs, n and 12 may pos- 

 sibly have been an earlier appearance of this condition. In several places 

 considerable emphasis has been placed upon the fact that portions of the spireme 



whether these were connections of any significance or merely portions of the 



segmentation at the periphery of the radiating loops, as found during second 

 contraction; this act being followed by a side-to-side approximation of the 

 limbs of the loops or of separate portions of the thread, thereby forming the 

 bivalent chromosomes. Evidences of spindle formation do not bear out 

 Lawsox's theory that the fibers are expressions of lines of tension due to the 

 contraction of the nuclear membrane. 



meres and linin, is still held by this investigator. Before definite conclusions 

 can be drawn concerning the structure of the resting nucleus and the formation 

 of the spireme from the resting condition, a closer series during the early pro- 

 phases and the late telophase of the last division of the sporogenous tissue must 

 be made. The careful measurements of the nuclear cavity and the chromatin 

 mass at the time of the first contraction cannot fail to show fallacies in the view 

 put forward by Lawson— Mildred Nothnagel. 



Periodicity in mitosis.— In a paper on embryonal growth and its diurnal 

 period, Karsten 1 " deals with the periodicity of cell division. He calls atten- 

 tion to the fact that many algae shed zoospores in the early forenoon, and there- 

 fore must have undergone cell division during the night; and he cites the work 

 of investigators who have shown positively that Spirogyra, Zygnema, diatoms, 

 and desmids divide at night, most of them between 9:00 p.m. and midnight. 

 He was not able to find similar records for the higher plants. The work of 

 Keixicott's on the periodicity of mitosis in Allium was overlooked. Karstex 



