336 BIOLOGY 



chromatin in order to make room for a similar amount brought 

 to it by the other of the two uniting sex cells. If, as we have 

 seen reason for believing, the chromatin contains the germ 

 plasm, this process has a most natural interpretation. The 

 maturation of the egg and the union of sex cells bring about 

 a new individual in which the germ plasm is a mixture from 

 two individuals (amphimixis) (Gr. amphi = together + mixis 

 = a mixing) . The result is that the germ plasm of the subse- 

 quent generations will be different from that which was pres- 

 ent in either of the parents of the last generation, since it 

 will be a mixture of the two, and, if the parents are in any 

 degree unlike, the mixture of their germ plasms will not be 

 exactly like that of either. It would be impossible for any 

 such complex things as two bits of chromatin to be mixed 

 twice without producing differences in the mixtures. In other 

 words, the following generation will show variations from the 

 last. Since, however, this mixed germ plasm will be handed 

 on to form the germ plasm of the next, and all following genera- 

 tions, it will follow that the variations which thus appear will 

 be handed on indefinitely by the. process of heredity, and such 

 new characters as appear from the mixture of two germ plasms 

 will remain fixed in the race. With the next reproductive gen- 

 eration this mixed germ plasm will again be combined with 

 another mixture from another individual, and still further 

 variations will appear. Successive generations will thus tend 

 constantly to be more or less unlike their parents. Sex union 

 of eggs and sperms, therefore, appears to be a device to bring 

 about variation and divergence from type. 



If this conclusion is correct, we should expect those organ- 

 isms which multiply by sex union to show a greater amount 

 of variation than those which multiply by the asexual process 

 of simple division; and this appears to be a fact. If a horti- 

 culturist wishes to preserve unchanged a type of plant which 

 he has found, he contrives to multiply the plant by the asex- 

 ual method of budding, grafting, or cuttings. As long as this 



