Origin of Sexuality 269 



'* Among all of these the gametes can sometimes conjugate, 

 sometimes develop individually, according to the surroundings 

 and relations; sexuality is found still undetermined as it were 

 in unstable equilibrium. That can be understood, since most 

 of the above-named algae stand, as isogamete forms, at a still 

 relatively low stage. In higher groups of the algoid kingdom 

 where oogamy dominates, sexuality has become a quite stable 

 arrangement." 



Again Klebs's observations on Protosiphon (99, 2: 256) show 

 that, if the temperature of the surrounding water be raised 

 from 20° C.^ — when abundant conjugation occurs — to 27° C, 

 gamete cells that are about to conjugate fail to do so, but 

 instead form a wall around themselves, and in time develop 

 into new plants. The same result is got in weak Knop's solu- 

 tion. And when the ripe gametes of Chlamydomonas are 

 darkened they develop parthenogenetically. These and many 

 similar facts suggest that slight changes in energizing stimuli, 

 either thermic, chemic, or lumic, may favor or prevent sex- 

 cell maturation, but yet that the gametes retain the power to 

 grow into new mdividuals. 



Even in the same genus varying differences may be observed. 

 Thus, in Spirogyra varians (99, 1: 70-71) and others, com- 

 mencing conjugate cells may, if placed in running water or 

 salt solutions, become parthenospores that develop new plants. 

 On the other hand, in S. nitida, S. maxima, etc., when cells 

 fail to conjugate in filaments where most of the cells do so, 

 they soon become discolored and disintegrate. 



So just as cell-division is a seasonal activity that depends 

 on the cooperation of environal factors, and seems to be due 

 to steady discharges or liberations from the center of the nucleus 

 or the nucleolus of cognitic energy, that drive apart and rear- 

 range the chromatin substance of each cell, in like manner 

 conjugation seems to be due to the establishment of unlike 

 or differently charged amounts of cognitic energy, and the 

 resulting attraction of the differently charged gamete cells 

 when a definite specific climax in such differently charged 

 states is reached. 



