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THE AMEBIC AX XATURALIST [Vol. LV 



roborated by other evidence. That the splashed classes 

 are not necessarily always deficient is sho^\^l by the 

 progeny of the blue-splashed X blue mating in Table I, 

 group 5, and of the blue X blue-splashed matings in 

 Table III, groups 1, 2 and 3. 



The latter fact suggests that possibly certain individ- 

 uals used in these matings carried recessive factors tend- 

 ing to cause low viability, which were linked to the factor 

 R. Until the fact of a differential viability is demon- 

 strated, however, it is useless to speculate on this possi- 

 bility. The reason for the deficiencies in the blue- 

 splashed and also in the white classes, therefore can not 

 at present be determined. 



IX. Identification of the Fo Genotypes 

 As indicated in my former paper (1918r/, p. 113) the 

 genotypes expected in the several Fo phenotypes from the 

 blue-splashed X recessive white crosses are as follows : 

 blue, PP(Re){rE) and Pp{Re)irE); blue-splashed, 

 PP{Re){Re) and Pp{Re){Re); black, PP{rE){rE) 

 and Pp{rE){rE) - white, pp{Re){Re), pp{Re){rE) and 

 pp{rE){rE). Although the limitations of equipment 

 wore such that comparatively few F^ individuals could 

 l)e tested, fortunately all of the genotypes but one have 

 been idt'iitified by making the appropriate crosses. The 

 l)lnes mated to individuals homozygous for p and E gave 

 blues and bhicks in equal numbers, or, blues, blacks and 

 whites in the approximate ratio of 1:1:2, as the case 

 might be. The blue-splashed mated to individuals of the 

 same constitution produced all blues, or, equal numbers 

 of l)Iuos and whites, depending upon whether or not they 

 wnc honicAyuous with respect to P. Similarly the blacks 

 ua\.' all 1)l;i('ks, of, blacks and w^hites, depending upon 

 tluMi- condition with respect to P. 



Tlir whitr.^ on tln> other liand were mated to blacks 

 known to ho hoino/,v-on> for /' and /v'. The pi>{Re){Re) 



