HEREDITY 



333 



cleanly after synapsis and a fragment of one may remain attached 

 to the other. Offspring from such gametes show either the total 



M 



A 

 B 



C 

 D 



U 



A 



\B 



C 

 \0 



SPERM A TOGONIUM 



SYNAPSIS IN PRIMARY 

 SPERMATOCYTE 



AFTER REDUCTION 

 DIVISION] ONE IN 

 EACH SECONDARY 

 SPERMATOCYTE. 



Fig. 208. — Diagram illustrating a simple case of an interchange of materials be- 

 tween two homologous chromosomes during synapsis. Obviously, all genes, such as 

 C, D, and c, d, that are detached and assumed by the synaptic mate are passed into 

 the succeeding generation together. Likewise all genes located in regions not de- 

 tached, such as A, B, and a, b, are inherited together. 



absence of a character, or else an exaggeration of the character. This 

 appears to be the cytological basis of one class of mutations. 



