No. 524] CHROMOSOMES AND HEREDITY 465 



no difference how the chromatin is assorted in the 

 chromosomes, so long- as the sum total of the materials 

 is present. 



From this point of view the individuality of the chro- 

 mosomes is a matter of secondary importance; for, the 

 same or equivalent material may he represented by two 

 or by forty chromosomes. Individuality or genetic con- 

 tinuity (i. e. f ontogenetic not phylogenetic) has no 

 further significance, from this standpoint, than that it 

 insures for each species the transmission to all the cells 

 of the body of a given amount of materials or possibly a 

 definite amount of all the different kinds. 



We may next proceed to examine into the relation of 

 the chromosomes in Mendelian inheritance from the 

 point of view reached in the preceding discussion. 



Chromosomes and Mexdelism 

 It has become generally accepted by students of Men- 

 delian inheritance that some kind of ''segregation" is 

 the key to the numerical results that play an all-impor- 

 tant part in the Mendelian theory of heredity. The dis- 

 covery that there occurs in the formation of the germ- 

 cells a process that supplies the machinery by means of 

 which segregation might take place has aroused expec- 

 tation to a high pitch of interest in the application of the 

 observations of cytology to the conclusions in regard to 

 Mendelian segregation. It is true that there is much 

 diversity of opinion as to the value of cytological study, 

 in its present imperfect state of development, to Men- 

 delism, and this divergence relates unfortunately to the 

 very nature of the processes involved. 



Mendel realized that the numerical proportions that 

 appear in the second hybrid generation could be ex- 

 plained, if, in the formation of the germ cells or gametes, 

 a separation of the constituent elements, or characters of 

 the hybrid occurs. These paired characters that separate 

 Bateson has called allelomorphs. 



A process takes place in the germ-cells, at the 

 so-called maturation divisions, that may possibly offer 



