THE LIFE CYCLE 363 



Objects. — The purpose of regeneration and grafting experi- 

 ments on animals has been to obtain new side Hghts on the 

 nature of the organism. Nature furnished the hints for 

 the first experiments tried. The rooting of detached 

 twigs of the crack wiUow might have suggested to anyone the 

 possible rooting of cuttings. The finding of regenerating star- 

 fishes, broken in the surf, might have suggested regeneration 

 experiments on animals, and if a portion of an animal's 

 body from which the sex organs were removed, were able, 

 as it is in fact in some cases, to reproduce the missing parts 

 with sex organs included, then the experiment w^ould seem to 

 have shown that the distinction between body plasm and 

 germ plasm is not to be too sharply drawn. Although the 

 sex cells would normally come from the sex organs removed, 

 they might come from new sources in the body. 



Study 44. Grafting practice with plants. 



Materials needed: Selected and over- wintered cions and 

 rooted seedlings or other stocks for their reception; grafting 

 wax (see appendix) and sharp pocket knives. 



It will be worth the time of a laboratory period for the 

 student to make with his owm hands the combination of 

 parts of two species, and later to see them growing as one. 

 Different types of grafting may be demonstrated also, and 

 the later matured results of previous operations. The work 

 should be directed by someone who has had practical 

 experience. 



The record of the study, should be an illustrated account 

 of the student's own operations and observations. 



Reserve potentialities of the living substance. — The studies 

 of this chapter should have been convincing of the wide 

 range of methods by which the ends of life — the preserva- 

 tion of races — are accomplished. We began this chapter 

 by speaking of the normal course of life, which is merely the 



