34 



BIOLOGIC BASIS OF SEX 



Avore nuult' i)ii 237 workers from hotcrozy- 

 gous mothers. For the chartreuse loeus. 12 to 

 20 per cent were homozygous, for x\w i\ory 

 locus 1.8 per cent, and (he cordovan locus 

 on lesser numbers per t-ent. An egg which 

 is destined to become an automictic worker, 

 a gynandromorph with somatic male tissue 

 or a mosaic male, is retained within the 

 queen for an unusually long time during 

 which meiosis is suspended in anaphase 1. 

 Normal reorientation of first division 

 spindle is i)ossibly inhibited by this aging 

 so that after the egg is laid meiosis II occurs 

 with two second division spindles on sejia- 

 rate axes as Goldschmidt conjectured for 

 rarely fertile rudimentary Drosophila 

 (19")7i. Two polar l)odies and two egg 

 prontich^i are formed. The polar bodies take 

 no fiu'ther part in develoinnent. In most of 

 the unusual eggs the two egg pronuclei 

 unite to form a diploid cleavage nucleus 

 which develops into a female. Rarely the 

 two egg pronuclei develop separately as two 

 haploid cleavage nuclei to form a mosaic 

 male. Two unlike haploid cleavage nuclei, 

 one descending from each of the two sec- 

 ondary oocytes after at least one cleavage 

 di\ision. unite to form a dijiloid cleavage 

 nucleus which develops together with the 

 remaintler of the haploid cleavage nuclei 

 to produce a gynandromorph with mosaic 

 male tissues. The male and female tissues 

 within these unusual gynandromor[ihs or 

 female types were identical with normal 

 drone or normal female tissues so were 

 probably haploid and diploid resiiectively. 

 Genetic segregation observed within the 

 mothers of automictic workers allows the 

 estimation of the distance between the locus 

 of the gene and its centromere. "With random 

 recombination and "central union" Tucker 

 estimates this distance for the chartreuse 

 locus to centromere as 28.8 units and for the 

 ivory to its centromere 3.6 units. Four lines 

 of bees of diverse origin all showed a low 

 percentage of automictic or gynandro- 

 morphic types produced from queens in each 

 line. Various chance environmental condi- 

 tions apparently influence the rate of pro- 

 duction of these types. However, there were 

 some females in two of the lines with higher 

 frequencies inciicating that innate factors 

 may have significant eft'ects on their fre- 

 quencies. Observations on Drosophila spe- 



cies — I), porthenogeuetica (Stalker, 1956b), 

 I). ))ia)njabeirai (INIurdy and Carson, 1959) 

 and D. nielanogaster (Goldschmidt, 1957) — 

 strongly suppt)i-t this A-iew. 



The [irohleni of si'x determination in Hal)- 

 rol)i'acon presently stands as a function of 

 multii)le alleles in one locus, the heterozy- 

 gotes being female and the azygotes and 

 homozygotes male. The occasionally diploid 

 males are regularly produced from fertilized 

 eggs in two allele crosses after inbreeding. 

 These diploid males are of low viability and 

 are nearly sterile. Their few daughters are 

 triploids, their sperm being dijiloid. Apis 

 probably follows the same scheme, as a 

 few cases of mosaics with diploid male tis- 

 sue are known and close inbreeding results 

 in a sufficient number of deaths in the egg 

 to account for diploid males which might be 

 formed. ^lormoniella (Whiting, 1958), how- 

 ever, shows that this scheme for sex determi- 

 nation does not hold for all Hymenoptera. 

 In this form diploid males may occur 

 through some form of mutation. They may 

 then develop from unfertilized eggs laid by 

 triploid females. In contrast to Habrobra- 

 con the dijiloid males are highly viable and 

 fertile. Their sperm are diploid and their 

 numerous daughters triploid. Virgin triploid 

 females produce 6 kinds of males, 3 haploid 

 and 3 dij^loid. Similarly ]\Ielittobia has still 

 a different and as yet unexplained form of 

 sex determination. Haploid eggs develop 

 into males. After mating many eggs are laid 

 which develop into nearly 97+ per cent fe- 

 males. The method of reproduction is close 

 inbreeding but no dijiloid males or "bad" 

 eggs are formed. The prol)lem of the sex 

 determining mechanism remains open 

 (Schmieder and Whitiuii, 1947). 



The silkworm, Bomby.r mori, differs from 

 Drosophila, Lymantria and the species thus 

 far discussed in having a single region in the 

 ^^' chromosome (Hasimoto, 1933; Tazima, 

 1941, 1952) occupied by a factor or factors 

 of high female potency. The strong female 

 potency has thus far been connnon to all 

 races. The chromosome patterns of the 

 sexes are like those of Abraxas and Lyman- 

 tria: males ZZ + 2A and females ZwV 2A. 

 The diploid chromosome number is 56 in 

 both sexes. Extensive, well executed studies 



