358 The Unity of the Organism 



series, and that in the very last division before the trans- 

 formation of the unripe cells into eggs and spermatozoa, a 

 separation of the chromosomes which united at synapsis oc- 

 curs, so that each egg and each spermatozoan gets the full 

 series of eleven, characteristic of the species, some, however, 

 being of maternal and some of paternal origin. 



In his first paper, Sutton merely mentioned Mendelian in- 

 heritance in connection with the chromosome scheme he had 

 considered. "I may finally call attention/' he said, "to the 

 probability that the association of paternal and maternal chro- 

 mosomes in pairs and their subsequent separation during the 

 reducing division . . . may constitute the physical basis of the 

 Mendelian law of heredity." : His second paper is devoted 

 to an elaboration of this suggestion. Mendel pointed out that 

 where attributes of hybrids behave in heredity in the peculiar 

 way discovered by him, if one of the constant characters, for 

 example, the dominating one, be designated by A and the other, 

 the recessive, by a, and the hybrid form in which the two are 

 combined by Aa, then these two differentiating characteristics 

 of the development series in the progeny of the hybrids will 

 give the formula: A -\- 2Aa -f- a. This comes about on the sup- 

 position that the uniting of these characteristics follows the law 

 of chance; that is, that a male hybrid with attributes Aa pairing 

 with a female hybrid having the same attributes, gives: 



aa 



or A -j- 2Aa -|- a, since AA and aa can be nothing more than 

 A and a as here used. 



What in essence Sutton did was to show that such a chromo- 

 some seheme as he had partly proved and partly conceived 

 to exist in the germ-cells of the lubber grasshopper, could be 

 brought under the identical expression that we have just seen 

 Mendel deduced for the attributes of peas. If, Sutton reasoned. 



