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BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



the normal disparity between the sexes is naturally accentuated. Never- 

 theless, the differences between calculated and observed ratios are small 

 in all the crosses except [6] and [7]. Even iu these two cases calculated 

 and observed results are qualitatirely harmonious. Both indicate a 

 large excess of males; but the observed excess is larger than tlie 

 expected one, especially in cross [7]. 



2. Coupling of Certain Sex and Somatic Characters in the 



Germ-cells. 



In certain other crosses among Lepidoptera, males and females occur 

 in their normal proportions, approximate equality, but there is a ten- 

 dency for the offspring which resemble one parent to be pi'edouiinantly 

 of one sex, those which resemble the other parent being predominantly 

 of the other sex. In the following crosses between a species and its 

 inelanistic aberration, Standfuss ('96) notes the predominance of males 

 among the offspring having the aberrant form, while females predomi- 

 nate among those which have the species form. 



In these cases, there is clearly an imperfect correlation between the male 

 sex-character and the aberrant form-character. Is such correlation con- 

 sistent with the doctrine of gametic difierentiation 1 It is ; correlation, 

 or "coupling," between members of different ])airs of characters is a 

 recognized Mendelian phenomenon. Tlius, Correns OOO) has shown that 

 in crossing Mathiola incana with M. glabra, those hybrid plants which 

 have villous leaves always bear pink flowers, and tliose which have 

 glabrous leaves bear white flowers. Leaf character and flower color are 

 in this case perfectly correlatod, or " coupled," so that they cannot be sepa- 

 rated in heredity. Similarly, though less perfectly, in the butterfly crosses 



