THE PROBLEM 37 



this manner in these multicellular forms there is no place 

 for death. In the passage from one generation to the 

 next no residue is left behind. Agamic reproduction and 

 its associated absence of death occurs very commonly in 

 plants. Budding and propagation by cuttings are the 

 common forms in which it is seen. The somatic cells have 

 the capacity of continuing multiplication and life for an 

 indefinite duration of time, so long as they are not acci- 

 dentally caught in the breakdown and death of the whole 

 individual in which they are at the moment located. Thus 

 virtually every apple tree in every orchard in this coun- 

 try is simply a developed branch or bud of some original 

 apple tree from which it was cut, in many cases centuries 

 ago. Apple trees cannot of their own unaided efforts 

 propagate either buds or cuttings. So, until the interven- 

 tion of man, some apple trees died natural deaths, somati- 

 cally speaMng, just as do the higher animals of which 

 we shall speak presently. But their cells were inherently 

 capable of better things, as was demonstrated when man 

 first cut off a shoot from an old apple tree and provided 

 it with a root by grafting.* Then it went on and made a 

 new tree. From it in turn cuttings were taken, and so the 

 process has continued to the present day. A part of the 

 soma of one generation produces the soma of the next 

 generation and goes on living indefinitely. 



A different mode of reproduction is characteristic 

 of higher multicellular animals, and in all but the lowest 

 groups is the exclusive method. A new individual is 

 started by the union of two peculiar cells of extraordinary 

 potentialities, called germ cells. These germ cells are of 

 two sorts, ova and spermatozoa. In bisexual orgajiisms 



* This provision of roots was not essential, only practically convenient. 

 The cutting vrould, if enough pains were taken, grow its own roots. 



