Evolution of Sex 353 



kind of division is very important as it is one which is later 

 adapted to high functions, in higher forms of heredity, and 

 always precedes sexual conjugation. It seems to show that 

 the impulse to divide continues in the centrosomes, and is, 

 under some circumstances inoperative toward the cytoplasm 

 or general mass; even while the nucleus is submissive and 

 responsive to the last degree of endurance. 



It appears in some cases that lack of nutrition, or per- 

 haps its exhaustion into the nucleus, extinguishes the cyto- 

 plasm and under these conditions the nucleus still divides 

 as impelled by the centrosomes. In the cell of scant and ex- 

 hausting cytoplasm, the centrosome still has energy to divide, 

 and to exercise its repulsion of its like; which continues to 

 the last possible division of the duplex nucleus into two 

 similar duplex nuclei; and then, when the centrosome di- 

 vides once more, the doubled chromosomes have no mole- 

 cular surplus to act upon; they are exhausted and instead 

 of separating themselves in the double form, they simply 

 split into the ultimate single primitive units; so that a cell 

 which usually shows four chromosomes, will in these final 

 divisions show only two chromosomes for each resultant cell. 

 The cell stands disrupted into four parts, each with the fun- 

 damental single chromosomes, constituted with the mini- 

 mum number of divisible units necessary for its molecular 

 character. This final unit appears as a result of exhaustion, 

 or of maturity, under conditions varying from that 

 normality which continues life without change. But there 

 arises from it, in the wonderful possibilities of natural selec- 

 tion, a function which raises life to a new plane. This func- 

 tion is sex. 



