182 



NUCLEOCYTOPLASMIC RELATIONS 



allele. Sometimes half the animal bilaterally is lemon lethal, and 

 the other half wild type, each region being autonomous. At other 

 times, certain portions of the body or head are lemon lethal with 

 the rest wild type; or the inverse occurs where only a small patch 

 of wild-type tissue is present on the adult animal. The lethal 

 effect of the gene is nonautonomous, and a male will eclose if 

 only a small patch of wild-type tissue is present. The hereditary 

 background necessary for production of the mosaics is not fully 

 understood at present; not all females of the lemon lethal stock 

 produce mosaics, but when one female is a mosaic producer she 



MOSAIC 



HAPLOID 



EMBRYO 



TWO PRONUCLEI FROM BINUCLEATE OOCYTE 

 (POSTULATED) 



TWO PRONUCLEI FROM UNINUCLEATE OOCYTE 

 (ACTUAL) 



Fig. 6. Representation of normal meiosis, meiosis in a binucleate oocyte, 

 and meiosis in which two meiotic products become pronuclei. 



tends to produce others. Gynandromorphs from virgins are rare, 

 but they also occur. 



In any event, the occurrence of a haploid mosaic male means 

 that the egg from which it originated was binucleate. In which 

 sense is it binucleate — two oocyte nuclei undergoing meiosis 

 side by side, or two meiotic products from one oocyte nucleus 

 becoming cleavage nuclei (Fig. 6)? In a cytological investiga- 

 tion of oocytes from females that produced mosaic males, no 

 more than one nucleus was observed in any developing oocyte; 

 however, in several cases, eggs were observed which were not 

 blocked at the first meiotic metaphase. Meiosis was continuing 



