22 Edmund B. Wilson 



E. The Differential Chromosomes in the Synaptic and Growth- 

 periods 



I will now briefly consider a very marked difference between 

 the sexes in respect to the behavior of the differential chromosomes 

 during the contraction-phase of synapsis and the succeeding early 

 growth-period. 1 In the male, as was fully described in my last 

 paper, both the heterotropic chromosome and the idiochromo- 

 somes condense early in the growth-period (usually as early as the 

 contraction-phase of synapsis) to form rounded, condensed, 

 intensely-staining chromosome-nuclei. In this condition they 

 persist throughout the whole growth-period of the spermatocyte, 

 without ever assuming the looser texture and more elongate form 

 of the other chromosomes. In the earlier part of this period they 

 are as a rule closely associated with a large pale plasmosome, but 

 later become separated from it. 



In the female no trace of such a chromosome-nucleus can be 

 found in the contraction-figure of the synaptic period. My best 

 preparations of this stage are from the ovaries of the larval Anasa, 

 which show a distinct synaptic zone of oocytes intervening between 

 the zone of multiplication and the growth-zone; but I have 

 observed the same condition in the ovaries of recently emerged 

 adults of Harmostes, Alydus, Euschistus, Coenus and Podisus. 

 In all these forms the contraction-figure is very similar to that of 

 the spermatocytes, the chromosomes being in the form of deeply 

 staining, ragged, and apparently longitudinally split loops that 

 are crowded into a spheroidal mass toward the center or one side 

 of the nucleus and surrounded by a large clear space. The nuclei 

 at this time occasionally show one or two small deeply-staining 

 nucleolus-like bodies (probably plasmosomes); but these are 

 much smaller than the chromosome-nuclei of the spermatocytes 

 at this period, and in many of the nuclei are absent. The contrast 

 between these nuclei and those of the male at the corresponding 

 period is so striking as to be at once apparent. In later stages the 

 chromosomes spread through the nuclear cavity, become looser 

 in texture and finally give rise to a fine reticular structure. In 



J A fuller presentation of observations on these phenomena is reserved for a subsequent paper. 



