110 JOHN H. SCHAFFNER Vol. XXII, No. 4 



DISCUSSION OF THE FOREGOING SERIES. 



From a study of the preceding series of species and their 

 numerous near relatives, from the lowest manifestation of 

 sexuality to the highest, it becomes evident that sexuality in 

 respect to its influence on the morphology of the vegetative 

 structures has been a gradual evolution making a slow and 

 almost uniform progress to the ultimate species, while the 

 evolution of the gametes, although also showing fundamentally 

 a similar progression, was attained very early, so that usually, 

 when one passes a little beyond the unicellular forms and simple 

 filaments, one finds the same general differences between eggs 

 and sperms as are present in the highest types. The most 

 remarkable thing about the whole evolutionary progression is 

 the fact that very rarely does any step in advancement have 

 any direct relation either to the reduction or to the fertilization 

 stage. So it comes about that the determination of the sexual 

 state takes place in the vast majority of cases in the vegetative 

 tissues, at other times than the periods of reduction and fer- 

 tilization. On the other hand, since hereditary factors are 

 apparently properties of chromosomes, the characters of the 

 individual outside of its sexual state are in the vast majority of 

 cases predetermined by reduction and fertilization. The 

 environment merely determines the degree of hereditary expres- 

 sion or the time of the expression in the life history. 



We can then postulate the phenomena of sexuality as dis- 

 tinct from hereditary units. Probably ordinary hereditary units 

 are irreversible properties of specific parts of the chromatin and 

 cannot be changed except by mutation, while sexual states 

 are due to fundamental properties of the protoplasm or its 

 secretions due to a chemical or physical condition of the mole- 

 cules or atoms and so any given organic structure may pass 

 from the female to the neutral and then to the male state, or in 

 any direction from one of these states to the other without any 

 change in the hereditary factors whatever. 



Cells may, therefore, be absolutely nonsexual or potentially 

 sexual. The potentially sexual may be in the male, female, or 

 neutral state in varying degrees of intensity. It has been the 

 practice of morphologists to designate individuals and genera- 

 tions in an antithetic cycle as "nonsexual" and there is no 

 special objection to this although "neutral" individual or gen- 



