Etmer on Growth and Inheritance 425 



jach contain: this it will be our business, later on, to 



mdeavour to point out. 



It is most true, as Mr. Cunningham says, that Professor 



Weismann's view of heredity is not, as he seems to think, 

 in any sense an explanation. Whether the reappearance in 

 offspring of characteristics possessed by parents be due to 

 iiny influence of a parental organism, or merely to a fixed 

 tendency in germ-plasm, it remains in either case equally 

 and absolutely unexplained. The use made of the word 

 ' heredity ' often shows that our contemporaries are as ready 

 as were any of their forefathers to rest content with mere 

 words and phrases. The term ' heredity ' merely serves to 

 denote the fact that characters remain constant, within 

 narrow limits, through succeeding generations. 



The persistence of characters implied by heredity is as 

 mysterious as, and no more so than, the process of change 

 which external conditions may induce. 



' Everybody knows that in a given district, even on a given farm, 

 certain varieties of animals and plants cannot be produced in perfec- 

 tion. Individuals may be procured, the most perfect in existence, 

 but in a particular district or on a particular farm they do not 

 *' thrive " ; that is to say, the qualities for which they are valued 

 disappear in the individuals, or, as is more often the case, in a few 

 generations, in spite of all care and selection, . . . there is evidence 

 that physiological change precedes morphological. There is a climbing 

 kangaroo in Papua which shows so little adaptation of structure to 

 the climbing habit that no naturalist would believe from the mere 

 study of its body that it lived in trees. Eut, as a matter of fact 

 it does live entirely in trees.' 



Professor Eimer's work consists of eight chapters, refer- 

 ring respectively to the following subjects. In the first we 

 have a brief exposition of the newest theories concerning 

 Evolution. The second treats of ' the organic growth of the 

 living world.' The third deals with the ' influence of 

 adaptation in the formation of species.' The fourth is 



