Chromatin us ''H credit artj Substance"' ^557 



into the structure and maneuvering of tlie eliroinosonies of 

 the germ-cells during the "ripening" of the germ-cells. The 

 facts usually taken as the starting ])oiiit for tlie livpothesis 

 are that all the cells, both body and germ, of an onliiiarv 

 sexual plant or animal have a constant numhc r of chromo- 

 somes, the number being characteristic for the sjjecies ; that 

 before fertilization, an essential feature of which is the 

 union of male and female chromosomes, the chromosome 

 number of both male and female cells is reduced hy oik' lialf, 

 excepting in those cases where there Is an odd or accessorv 

 chromosome, so that the union of tiie cliromosomes In ferti- 

 lization restores the number ty[)ical of the species: tliat tlje 

 final adjustment gives the fertilized Qgg and all the cells 

 arising from it supposedly equal portion of chromatin from 

 each parent; and finally, that the chromosomes of the germ- 

 cells in many animals, if not in all, are not all alike either 

 in form or size. 



Proceeding from these facts Sutton studied the genn-cells 

 of the lubber grasshopper w^ith reference to the question of 

 whether the differences in size and form of the chromosomes 

 are haphazard and meaningless or have some constancy, 

 especially in relation to their maternal and paternal sources, 

 and in the way they couple with one another in fertilization. 

 Summarizing the results for the germ-cells as they grow 

 and multiply before the ripening process sets in, he con- 

 cluded that during this period the chromosome group of 

 each germ-cell is composed of two equivalent chromosome 

 series, each series consisting of eleven chromosomes diff'i ring 

 among themselves in size, and that in all probability one of 

 these series comes from the father and the other from t he 

 mother. Furthermore, he believed that the reduction In 

 number which takes place in this ripinlng sta^e and is known 

 as synapsis, is accomi)llshed by the union of two series in 

 such fashion that each member of the maternal series unites 

 wuth one of corresponding size, its mate of the patirnal 



