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THE AMERICAN NATURALIST [Vol. XLIV 



forms, as is assumed in so many of the most recent spec- 

 ulations concerning sex. This topic will come up later 

 for fuller consideration. 



As I said, the presumption is that the regenerated 

 protonemata from this sporophyte have the diploid 

 number of chromosomes, and when the spores are formed 

 the number is reduced. Have the sex characters sepa- 

 rated when the chromosomes are reduced! We have no 

 means of knowing, but two important points should be 

 noted: first, that the male or the female is produced with 

 the reduced number of chromosomes present; second, 

 that an approach to the same result is reached in the re- 

 generated forms with the entire number present. Sex 

 here is not connected with the half number, or the whole 

 number. Any attempt to solve the problem of sex in the 

 mosses along these lines must assume that some unknown 

 or unseen chromosomal element is separated at the time 

 of formation of the spores. 



Furthermore, since hermaphroditic species of mosses 

 and ferns produce both male and female gametes on the 

 same plant that has the reduced number of chromo- 

 somes, it would be necessary to assume in such cases that 

 some kind of chromosomal separation takes place in dif- 

 ferent regions of the same protonema to give rise to 

 male or to female organs. The only other alternative 

 would he to assume that the kind of gamete formed, 

 male or female, is determined by the regional differences 

 in the protonema or prothallium, and that no separation 

 of chromatin precedes this effect. If such effects can be 



this topic again. 



Blakeslee's brilliant experiments with moulds also 

 bring out many important points connected with sex de- 

 termination, although nothing is known as yet concern- 



them) and that these produce non-sexual spores of the 

 same sex indefinitely. Other mycelia are female ( + 



