Heredity and sex . rgans arepresent. The third condition is called Parthenogenesis —a condition in which the eggs of an animal or plantdevelop without being fertilized. GYNANDROMORPHISM Gynandromorphs occur most frequently, in factalmost exclusively, in insects, where more than onethousand such individuals have been recorded. Theyare most abundant in butterflies, common in bees(Fig. 81) and ants, rarer in other groups. Theyoccur relatively more often, when two varieties, orspecies, are crossed, and this fact in itself is signifi-cant. A few examples will bring the cases before us. In my cultur
Heredity and sex . rgans arepresent. The third condition is called Parthenogenesis —a condition in which the eggs of an animal or plantdevelop without being fertilized. GYNANDROMORPHISM Gynandromorphs occur most frequently, in factalmost exclusively, in insects, where more than onethousand such individuals have been recorded. Theyare most abundant in butterflies, common in bees(Fig. 81) and ants, rarer in other groups. Theyoccur relatively more often, when two varieties, orspecies, are crossed, and this fact in itself is signifi-cant. A few examples will bring the cases before us. In my cultures of fruit flies several gynandro- 161 162 HEREDITY AND SEX morphs have arisen, of which two examples are shownin Fig. 82. In the first case the fly is female on oneside, as shown by the bands of her abdomen, and maleon the other side (upper right-hand drawing). In the second case the fly looked like a female seenfrom above. But beneath, at the posterior end, thegenital organs of the male are present, and normal. Fig. 81. — A gynandromorph mutillid wasp, Pseudomethoca canadensis,male on right side, female on left side. in structure. In the latter case the fly is ostensiblya female, except for the male organs of reproduction. How can we interpret these cases? We find aclue, I think, in the bee. It is known that if the eggof the bee is fertilized, it produces a female — onlyfemale-producing sperms are formed. If it is un-fertilized, it produces a male. In the bee two polarbodies are produced, and after their extrusion the num-ber of chromosomes is reduced to half, as in ordinarycases. The haploid number produces a male; thedouble number produces a female. Boveri pointed out that if through any chance the GYNANDROMORPHISM 163 entering sperm should fail to reach the egg nucleusbefore it divides, it may then fuse with one of thehalves of the egg nucleus after that divides. From the
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjectsex, bookyear1913
