99 



special sensiti\ily and polarit\' to cmironal stimuli (p. 121); 

 these plastids evolved in the probable order of Icucoplastids 

 (chemoenergids), helioplasts (chromoplasts and chloroplasts) 

 or photoenergids, geoplasts (geoenergids), thigmoplasts (me- 

 chano-energids), and parohelioplasts, which "are only known in 

 their energizing results, not as yet as definite structures. Thus 

 for ever}' class of physiological function there is postulated by 

 the author, not only a particular kind of energy, but also a 

 particular structure. Some of these structures are known 

 only by inference from a given function. This granular philos- 

 ophy is extended to include the notion that there is "a large 

 series of bodies common to all plants . . . which can at any 

 time be gradually reproduced by the joint action on, and re- 

 action of protoplasm and its related ferments under the more 

 fundamental action of appropriate environmental stimuli." 

 These bodies may at times be reduced to ultra-microscopic 

 bodies (p. 150). This conception would appear to be a form of, 

 or analogous to, pangenesis. Its acceptance, according to the 

 author, leads logically to a rejection of the concept of "acquired 

 characters," and therefore the troublesome problem of the 

 inheritance (or otherwise) of acquired characters vanishes. 



In the discussion of heredity, on pages 175-179, no reference 

 is made to much modern work — Spencer's definition, for example, 

 being quoted, but no reference made to Johannsen's fruitful 

 definition and studies. Johannsen's definition, "the appear- 

 ance, in successive generations, of the same genotypical con- 

 stitution of the protoplasm," is suggested by the author's 

 definition: "the like continuity of molecular structure in relation 

 to like outgoing and incoming currents of energy, so long as a 

 body is exposed to the same environment, or to an environment 

 that, within definite limits, fails to alter its average constitu- 

 tion" (p. 179). This definition involves the conception that 

 variation, or disturbance of heredity (p. 178) is "due to changed 

 environal condition," which is the prevailing conception of 

 geneticists as to the cause of variation. On page 187 both 

 heredity and variation are defined in terms of energy. 



The theory is maintained (p. 301, and elsewhere) that "the 



