The Spermatogenesis of HviiRin Peas 525 



side of the vacuole ; when it enters into the synapsis stage it is 

 probably already in the form of a continuous spireme. It is much 

 bent with short turns and appears usually to be homogeneous and 

 not split ; the spireme at this time closely resembles the much 

 convoluted thread with its short, sharp turns as it emerges from 

 the synapsis stage. Since the chromatin assembles in a spireme 

 before the so-called synapsis condition the significance of the 

 latter is not apparent in these forms. 



The cytoplasm of the spore mother-cell is reticular and it 

 always, from the spore mother-cell to the tetrad, retains this 

 structure. In this regard the pea is very different from the cotton 

 hybrid in which kinoplasm forms a marked character of the cyto- 

 plasm in the more advanced stages of spore formation, and from 

 some of the homologous cells of Syringa RotJioniagcnsis * in which 

 kinoplasm is strongly developed. The exaggerated development 

 of kinoplasm or filar-plasm in the cytoplasm of the spore mother- 

 cells is therefore not a constant or diagnostic feature of hybrids. 



Although I did not study closely the origin of the achromatic 

 figure, I observed that it is derived from a multipolar one. The 

 multipolar spindle originates in groups of fibers which are placed 

 near the outer edge of the cytoplasm and which radiate from a 

 common point towards the nucleus. The place of genesis of the 

 achromatic figure is therefore very different from that of the cot- 

 ton hybrid, and the structural reason appears to lie in the presence 

 in the latter, and absence in the former, of a dense perinuclear zone 

 of cytoplasm. The achromatic figure in cotton originates inside 

 of this perinuclear zone, which thus appears to inhibit its more 

 peripheral origin. It may also be that the zone of denser cytoplasm 

 which in the cotton closely surrounded the nucleus not only formed 

 a limiting boundary for the spindle, but at the same time made 

 necessary for the mechanical support of the cell the formation of 

 an outer layer of kinoplasm, and that its absence in the pea not 

 only changed the structural relations of the parts of the cell but 

 altered the mechanical condition as well, making the formation 

 of the kinoplasmic layer unnecessary. 



The first maturation mitosis is heterotypic. The chromosomes in 

 the metaphase are not different from those in the pure races Fillbasket 



*Juel, H. O. See bibliography. 



