HEREDITY 



b; (ba. 



(B RA) = Agout; (Teuersion) 



®\ (RA) (ba) (R)Gamete5 



(eg) @a) (ig) (Qba) 



1 I I I 



Agouti Agouti Agouti Agouti (fixed) 



Black Bed Black 

 Bed 



4 2 2 1 



Fig. 35. — Diagram to show the gametic combination and re- 

 combinations which occur in the production and fixation of 

 an atavistic coat-character in guinea-pigs. 



Row 1 shows the character of the gametes formed by the 

 parents crossed; row 2 shows the character of the Fi agouti 

 individuals resulting from the cross; row 3 shows the two 

 different sorts of gametic splittings which may occur in the 

 production of gametes by the Fi agoutis, and how four differ- 

 ent kinds of gametes result; row 4 shows how among such 

 gametes four different kinds of unions may occur that will 

 produce agouti young. The BA-BA combination, it will 

 be understood, could result only from the union of a BA 

 gamete with another gamete of like constitution. Below 

 each of the four combinations is indicated the kinds of young 

 which an animal of that sort would produce if mated with 

 an animal like itself. The numerals show the expected 

 relative frequencies of the four sorts of combinations. 



66 



