Feb., 1906,] Sexual and Nonsexual Generations. 
473 
SEXUAL AND NONSEXUAL GENERATIONS. 
John H. Schaffner. 
Recently a number of ideas have been put forward by 
various authors as to what is a sexual or nonsexual individual 
or generation. To the writer the case seems to be a matter of 
definition. The confusion appears to arise not so much in a 
misapprehension of the facts involved as in the extension of the 
meaning of the terms used. But in this case individuals and gen- 
erations should be judged by what they produce. 
A sexual generation is a gamete-producing generation. Any 
individual, therefore, producing cells which normally are to 
conjugate possesses sexuality provided the conjugation results 
in reproduction. If there is a differentiation of sex, the indi- 
vidual which produces female gametes directly is a female indi- 
vidual, and the individual which produces male gametes directly 
is a male individual. The gametes or male and female cells may 
be produced with or without a preceding reduction division, for 
the sexual generation may be either an “a:” or a “2v” generation. 
A nonsexual generation is a spore-producing generation, the 
spores being non-conjugating reproductive cells. The non- 
sexual generation may also be either an x" or a “2x” genera- 
tion. Sex terms are, of course, not to be applied to nonsexual 
generations or individuals. 
An alteration of generations may be antithetic having an 
“x” gametophyte and a “2x” sporophyte. And certainly the 
generation which produces the sexual cells is to be called the 
sexual generation and the one producing the nonsexual spores 
the nonsexual generation. So in the higher as well as in the 
lower plants the gametophyte is the sexual generation and the 
sporophyte the nonsexual. An alternation of generations need 
not be antithetic. But both generations may have the x'" 
number of chromosomes. In such forms as Oedogonium and 
Coleochaete, for intsance, where the 2x number of chromosomes 
appears to be only in the zygote, the organism coming through 
reduction from the zygote is still the sporophyte and nonsexual 
generation for the reason that it finally produces nonsexual 
spores. It is possible that there are “2x,” sporophyte genera- 
tions producing their spores without reduction which v.'ould 
then occur before the formation of the gametes and we would 
then have an alternation of generations with a “2x” gameto- 
phyte and a “2a;” sporophyte. Here again the gametophyte is 
the sexual and the sporophyte the npnsexual generation. In 
other words, sexual and nonsexual individuals or gametophytes 
and sporophytes are not determined by an .v number or a 2x 
number of chromosomes but by the fact that the first produce 
gametes and the second nonsexual spores. 
