Xo. 524] 



CHROMOSOMES AND HEREDITY 



483 



The experiments of Elie and Emile Marchal on dioe- 

 cious mosses are equally interesting. They used species 

 with separate sexes. When spores from a single capsule 

 are sown some produce female, others male protonemata. 

 The sporophyte generation that produces the spores has 

 arisen from a fertilized egg; the formation of the spores 

 is a non-sexual process. The sporophyte contains the 

 full number of chromosomes, and this number is reduced 

 to half in each spore, not by union of chromosomes, but 

 by halving the total number. 



The protonemata or gametophytes produce the male 

 or the female organs separately. Fragments of a pro- 

 tonema regenerate a new individual having always the 

 same sex, under all the possible external conditions to 

 which the Marchals subjected them. Obviously the sex 

 of the protonema once determined can not be changed, 

 and the presumption is in favor of the view that the sex 

 of each spore is determined at some time in its forma- 

 tion. 



The tissues of the sporophyte itself should contain the 

 potentiality of both sexes. Owing to the power of re- 

 generation possessed by this tissue, it is possible to test 

 such a view. Pieces of the sporophyte regenerate pro- 

 tonemata— each thread arises from a single cell of the 

 piece; a cell presumably having the full number of chro- 

 mosomes. These regenerated protonemata produce 

 moss plants that are either male, or female, or herma- 

 phroditic. They seem to be all potentially hermaphro- 

 dites, but in some plants only the male organs develop — 

 especially those that first appear; in other plants only 

 female organs. If the suggestion just hazarded is cor- 

 rect, namely, that all the plants are hermaphroditic, and 

 the males and females are due to the failure of the other 

 sex to develop, we raise a large issue; namely, whether 

 males and females may not in general be potential her- 



