imi^Y imui KZ/IVADA.^3TAT0SZS W THE F. 310. OF ZEA MAYS L. 165 



nature, quickly increase at the synapsis indicates that at this 

 stage the metabolic activities are suddenly increased. It is not 

 impossible that a sudden change of the osmotic equilibrium 

 caused by the metabolic activities is the chief physiological 

 cause of the synaptic contraction (2, P. 270). 

 ' On the advancement of the nuclear development the seg- 

 mentation of threads takes place, in which the double nature of 

 threads is clearly seen (Fig 5). The formation of spindle fibres 

 around the nucleus is observed already at this stage. The 

 segments or gemini newly formed are mostly of the form of 

 twisted ropes, but they gradually take the form of a ring or 

 a rod, as the contraction of each segment proceeds (Fig. 6). 

 Since the segmentation takes place, however, not simulta- 

 neously, the stage of development is different in different 

 gemini. The one takes a ring or rod shape, while the others 

 are still on the way of segmentation (Fig. 5). As soon as the 

 nuclear membrane disintegrates, at first the tripolar spindles, 

 later the bipolar are formed as usual, but pretty often I have 

 met with the case in which the bipolar spindles are formed 

 from the first. In the latter case the gemini are arranged in a 

 line along the spindle, and the appearance is somewhat 

 irregular. At the tripolar stage of the spindle a pretty large 

 nucleolus is often still found between the gemini (Fig. 24). 

 Through all the stages of development there are many small 

 granules in the cytoplasm, which are stained with Heiden- 

 hain's hasmatoxylin or safranin just like chromatin granules. 

 The granules appear to become larger at the later stage and 

 in the heterotype as well as the homotype division they often 

 appear most abundantly and crowd mainly around the nucleus, 

 so that at the disintegration of the nuclear membrane they 

 enclose the kinoplasmic area of the nuclear division. In one 

 preparation of * Amber rice pop corn ' these granules were 

 found in a great quantity at the heterotype division^ They 

 ctowded here and there in cytoplasm, so closely that under a 

 lower magnification they were mistaken for chromosomes. 



The peculiarities of the heterotype division in different 

 races are described in the followinsf. 



