GAMETOGENESIS 



473 



by way of chromosomes only from their grandparents. For their parents 

 are simply, as it were, the 'guardians' of their grandparental chromosomes 

 which, following the synapsis phase of growth (the final stage of the pre- 



FIG. 423. CHROMOSOME GROUPS OF SCHISTOCERCA DAMNIFICA. 



(A) Diploid chromosome group of dividing spermatogonium of Schistocerca, 

 showing the 11 pairs of chromosomes, and the unpaired (10-x) accessory chromo- 

 some. (B) Haploid group of primary spermatocyte, showing 11 bivalent chromo- 

 somes and the accessory (10-x). The 11 bivalents fall into a series with the same 

 size relationships as the pairs of chromosomes in the diploid group. (C and D) 

 Chromosome groups of secondary spermatocytes, one (D) with 11 univalent 

 chromosomes, like those of the diploid pairs, the other (C) with similar chromo- 

 somes, plus the accessory (x). All mature eggs presumably contain 12 chro- 

 mosomes, homologous with C. 



vious fertilization which resulted in the parents) become redistributed in 

 various combinations in the maturing germ cells from which the offspring 

 develop, and determine their hereditary possibilities. In other words the 

 germ-plasm is a continuous substance handed on from generation to gen- 



