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THE AMERICAN NATURALIST [Vol. XLIII 



hand with these modifications there appear male secondary 

 sexual characters in the female as more or less rudimentary- 

 male genital appendages at the end of the body. It would seem 

 to follow that the female is heterozygous, a fact of some general 

 interest. The discovery raises once more the question of the 

 cause of gynandromorphism in insects, for obviously these 

 hybrid moths show adumbrations at least of such a condition. 

 In this connection it is of interest to give Raepke's summary of 

 Standfuss's results regarding the sex of hybrid moths and the 

 occurrence amongst them of gynandromorphism. 



He classifies the results under five headings: 



First, those hybrids that are so abnormal (atypic or sexless) 

 that their sex can not be determined. 



Second, those hybrids in which only one sex develops, 

 Generally the male; females also rarely appear, but these so im- 

 perfect that reproduction is impossible. The males also are 

 sterile. 



Third, those hybrids in which both sexes appear in normal 

 proportions ; the females sterile, the males crossed back to the 

 parent species fertile in various degrees. The offspring of such 

 a union are, however, very abnormal and monstrous both in their 

 primary and in their secondary sexual organs. In certain series 

 <l!pi(i ml roniorpJis appear in surprisiiighj lare/e numbers. 



Fourth, those hybrids in which the females although appearing 

 normal lay either no eggs or abnormal eggs. The males are 

 like those in the last category or like those in the next. 



Fifth, those hybrids in which the females produce fertile eggs. 

 These eggs produce only embryos or if the caterpillar stage is 

 reached at all the young are weak. Whenever it has been pos- 

 sible to rear moths by crossing back these females to the parent 

 species (or from the male hybrids of the same cross) only males 

 develop but in such scanty numbers that they have not been 

 tested further. 



Whether in the last instance only males are produced because 

 they are hardier than the females or because of some more 

 fundamental relation is not evident from the results. 



On the other hand the italicized statement in the third cate- 

 gory calls for further examination. What is the cause of the 

 production of so many gynandromorphs? 



Two hypotheses have been suggested in recent years along 

 cytologieal lines that offer at least a formal solution of the 

 problem. Boveri suggested that the entering sperm fuses not 

 with the female pronucleus, but with one of the nuclei derived 



