92 



Edmund B. Wilson 



IV 



Female groups (by inference only) with two more chromosomes than the male. 

 In the male a pair of unequal idiochromosomes, half the spermatozoa receiving 

 both these chromosomes, and hence two more than the other half. In the female 

 (by inference only) two such pairs. 



FERTILIZATION FORMULA 



Egg 5 (including/,;) + spermatozoon^ — 2 = zygote n — 2 (including J, /) c5^ 



Egg V; (including 7, ;') + spermatozoon ?J including/,;) = zygote n (including I, I, i, ;',) $ (by 

 inference only) 



Described Case 



V 



Female groups with three more chromosomes than the male. Half the sperma- 

 tozoa receiving three more chromosomes than the other half. 



Egg ^ + spermatozoon^ ~ 3 ~ zygote n — 3 (d^) 

 Egg ^ + spermatozoon ^ = zygote « ( ? ) 



Described Case 



At least two of the foregoing types may be complicated by the presence of certain 

 additional chromosomes, present in some individuals but not in others of the same 

 species, to which I have appHed the name of "supernumerary chromosomes."^^ 

 The number of these varies from one to six in different individuals but is constant 

 in the same individual. In some forms (Metapodius, Banasa) these supernumer- 



'' Wilson '07b, '07c. A detailed description is now in preparation. 



