OLD TYPES AND NEW 



147 



This distinction between atavism and reversion 

 becomes clearer by illustration. 



If heterozygous brown-eyed individuals mate, 

 there is one possibility in four that their offspring 



c^;S^^>9 



Grandmother grandfather 



.t*oMOr, 





%lu}\^ Duplex 



HorflOZYGOTE HOMOZYGOTE 



Duplex'j 



/ 



I 



Heterozygote \ ^ 

 ' Simplex ^ 



1 \^v^ ^' Sim'plexX 



I ■ » ~1 I > "^ T |/\f A V 1 f"!^ ^- ■ -^ * 



^02Y&° 



'^t^/liplei^ 



HETfROZYGOTE HOMOZYGOTE HETEROZYGOTE 

 Simplex Duplex 5/mplex 



Fig. 48. — Three generations of a Mendeliau monohj^brid. The outlines 

 represent the somatoplasms with the phenotypio character on the out- 

 side. The black symbols inclosed within the somatoplasm stand for 

 the germplasm in the form of gametes. The short dotted arrows indi- 

 cate the relation between germplasm and somatoplasm. The long 

 dotted arrows indicate possible recombinations of germplasms. 



will have blue eyes unlike their own, but like the two 

 blue-eyed grandparents. Such a blue-eyed child 

 would be an instance of atavism. The explanation 



