No. 504] NOTES AND LITERATURE 



815 



anlagen for the sex-characters into separate germ-cells in the 

 sense that into one animal wander testes-anlagen (determinants 

 of Weismann) and into another ovary-anlagen. This as far as 

 we know is not the case. Both germ-cells carry both sets of sex- 

 characters, as experiments with hybrids abundantly show. That 

 a germ-cell has male or female sex-tendency means only that the 

 male or female anlagen are in condition of capability to develop. 

 As to how one anlage in the germ-cells becomes active and the 

 other is brought to a latent condition we have no positive knowl- 

 edge. 



One may entertain several possibilities respecting the time 

 that sex is determined. He may take the position that the germ- 

 cells have held from the beginning the tendency to develop into 

 one or the other sex — which sex becomes apparent when caused 

 to develop by artificial parthenogenesis — and that the tendency 

 remains unchanged by fertilization; in other words, that the 

 germ-cells are unalterably fixed as to their sex-tendency and thus 

 independently determine the sex of their offspring pure: "pro- 

 game" determination. Either all the sperm or all the eggs are 

 so determined or only a part of each. Such predestination is 

 commonly ascribed to the egg, and the sperm is thought to be 

 without influence. Accordingly, half the eggs must be male and 

 half female in tendency. 



The second position ascribes to the germ-cells before fertiliza- 

 tion no fixed tendency to develop into a particular sex, and holds 

 that only at fertilization is the decision made as to what sex the 

 offspring shall have: pure "syngame" determination. 



According to the third position the product of the union of 

 the two germ-cells has no fixed sex-tendency. External in- 

 fluences determine only during the later stages of development 

 what the sex of the offspring shall be: pure "epigame" deter- 

 mination. Theoretically an "epigame" alteration of sex must 

 be possible, since the embryo contains both sex-anlagen. All 

 critical investigations, however, both zoological (0. Schultz) and 

 botanical (E. Strasburger), indicate that the means thus far em- 

 ployed in attempting to produce an alteration of sex-tendency 

 have yielded no significant results respecting the actual separa- 

 tion of sex-organs among different individuals. Primarily, at- 

 tempts must be made to determine whether the germ-cells of 

 unisexual forms have an indifferent sex-tendency or whether 

 they have a fixed tendency. If the latter condition prevail, it 



