822 THE AMEBIC AN NATURALIST [Vol. XLII 



differentiating characters, as in the great majority of the 

 dioecious Metazoa and man, there appears nothing to contravene 

 the facts and hypotheses regarding sex-determination as pre- 

 sented in the foregoing description of the experiments with cer- 

 tain of the higher flowering plants. However, such cases as are 

 presented by the aphids and the honey-bee, where all fertilized 

 eggs develop into organisms of like sex, are disconcerting from 

 the view-point of the above facts. Correns proposes that the 

 drone eggs of the honey-bee are incapable of fertilization (de- 

 velop parthenogenetically) . He inclines also to the idea that 

 all the eggs may have the male sex-tendency and that femaleness 

 dominates. But since all fertilized eggs develop into females 

 this necessitates, on the hypothesis that there are two kinds of 

 sperm-cells, the further assumption of selective fertilization. 

 The recent discoveries of Meves, Stevens and Morgan, that during 

 spermatogenesis -of the honey-bee, certain aphids and phylloxera, 

 respectively, one half of the spermatozoa degenerate (and these 

 probably are the male-producing kind) now brings these cases 

 into very close harmony with Correns 's observations on plants. 

 Thus all fertilized eggs must develop into females. The dis- 

 turbing question still lvmains as to just how a parthenogenetic 

 female aphid can produce male offspring. 



Again when two kinds of eggs are produced, as by phylloxera, 

 daphnids and rotifers, the larger invariably develop (partheno- 

 genetically) into females and the smaller into males. Correns 

 believes that here a proportion of the eggs may have become 

 altered ("umgestimmt") in sex-tendency and that their size- 

 difference stands in correlation with the difference in size of the 

 female and male individuals. In phylloxera this difference, 

 however, does not seem significant. Dinophikis apatris seems 

 to be a real exception to the hypothesis that sex is determined 

 by the spermatozoon. Nevertheless, Correns suggests that a 

 portion of the eggs, in consequence of a subsequent alteration or 

 originally, may have retained the male sex tendency ; or selective 

 fertilization may obtain, so that only the larger eggs are fertil- 

 ized by female producing spermatozoa and the smaller by male 

 producing. However, when caused to develop parthenogenet- 

 ically large and small females appear, the difference in size of 

 the eggs being related to size differences of the offspring and 

 may have arisen through ' ' prospective ' ' adaptation. This argues 



