SEX 355 



was that of Geddes and Thomson (1889), namely, that the two sexes 

 differ primarily in the character of their metabolism, the female sex 

 being characterized by the preponderance of anabolic processes and the 

 male sex by those essentially katabolic in nature. This conception is 

 important not only in connection with the question of sex control, but 

 chiefly with respect to the more fundamental problem of the nature of 

 sex itself. 



The long early period during which sex was looked upon as a character 

 more or less under the control of the environmental factors was succeeded 

 by one in which it came to be regarded as something automatically 

 regulated by some mechanism or condition within the cell, and as rela- 

 tively unalterable by external agencies. This conclusion, definitely 

 reached by Cue'not (1899) for animals and by Strasburger (1900) for 

 plants, received the support of a number of experimental researches on 

 animals and dioecious plants. Some of the latter will first be mentioned. 



It was found by Blakeslee (1906) that in certain strains of a mold, 

 Phycomyces, there are produced in the germ sporangium two kinds of 

 asexual spores, which give rise to "plus" and "minus" mycelia respec- 

 tively. The "plus" (male?) mycelium later produces spores which 

 develop only into "plus" mycelia and so on indefinitely, while the 

 "minus" (female?) strain perpetuates only the "minus" condition: in 

 both cases the sex seems to be fixed by some mechanism functioning at 

 the time of spore formation. 



In certain dioecious mosses (l. and fim. Marchal 1906, 1907) two 

 kinds of spores are produced in equal numbers in the capsule. Those of 

 one kind develop into male gametophytes (bearing antheridia only) and 

 those of the other kind produce female gametophytes (with archegonia 

 only). In no way were the Marchals able to alter the sexes of these 

 plants. Furthermore, new gametophytes formed by regeneration from 

 the old ones were just as rigidly fixed as to sex. Protonemata regenerated 

 from the tissue of the sporophyte, however, gave rise to leafy branches 

 bearing both antheridia and archegonia. Both sex potentialities were 

 therefore present in the sporophytic tissue and in the diploid game- 

 tophytes regenerated from it, whereas the normal haploid gametophytes 

 produced from spores were either purely male or purely female. 1 The 

 gametophytes of Marchantia (Noll; Blakeslee 1906) are similarly fixed 

 as to sex: if propogated repeatedly from gemmae the sex in any given line 

 remains the same in spite of alterations in the environmental conditions. 

 In Sphoerocarpos Douin (1909) and Strasburger (1909) were able to show 

 that two spores of a single tetrad produce male gametophytes while the 

 other two produce females. 



The obvious conclusion to be drawn from the above cases is that in 

 such forms a separation of the sexes takes place during sporogenesis. 



1 Diagrams of these experiments are given by Morgan (1919o, pp. 152-3). 



