NOTES 



Note 1 (p. 3). 



I HAVE been careful to speak of the ' appearance ' of cyclical 

 evolution presented by living things ; for, on critical examination, 

 it will be found that the course of vegetable and of animal life 

 is not exactly represented by the figure of a cycle which returns 

 into itself. What actually happens, in all but the lowest 

 organisms, is that one part of the growing germ (A) gives rise 

 to tissues and organs; while another part (2>) remains in its 

 primitive condition, or is but slightly modified. The moiety A 

 becomes the body of the adult and, sooner or later, perishes, 

 while portions of the moiety E are detached and, as offspring, 

 continue the life of the species. Thus, if we trace back an 

 organism along the direct line of descent from its remotest 

 ancestor, B, as a whole, has never suffered death ; portions of 

 it, only, have been cast off and died in each individual offspring. 



Everybody is familiar with the way in which the ' suckers ' of 

 a strawberry plant behave. A thin cylinder of living tissue 

 keeps on growing at its free end, until it attains a considerable 

 length. At successive intervals, it developes buds which grow 

 into strawberry plants ; and these become independent by the 

 death of the parts of the sucker which connect them. The 

 rest of the sucker, however, may go on living and growing in- 

 definitely and, circumstances remaining favourable, there is 

 no obvious reason why it should ever die. The living substance 

 B, in a manner, answers to the sucker. If we could restore 

 the continuity which was once possessed by the portions of 

 B, contained in all the individuals of a direct line of descent, 

 they would form a sucker, or stolon, on which these individuals 

 would be strung, and which would never have wholly died. 



A species remains unchanged so long as the potentiality of 

 development resident in B remains unaltered ; so long e.g. as the 



