2 28 POPULAR SCIENCE MONTHLY. 



Mendel's laws are of much practical importance because they make 

 plain to breeders of economic plants and animals that they can not 

 do what has been attempted so frequently, make improved breeds by 

 combining the divergent characters of close-bred varieties. The Men- 

 delian facts are of general evolutionary interest, not because they ex- 

 plain descent, but because they are incompatible with the commonly 

 accepted static theories of development which hold that evolutionary 

 progress is due to external or environmental influences and overlook 

 the independent self-caused motion of species. More detailed presenta- 

 tion of the latter view can not be undertaken here;* it must suffice for 

 the present to have pointed out that cytology has not proved the uni- 

 versality of Mendel's laws as 'principles of inheritance,' nor do the 

 laws prove that the chromosomes are the long-sought 'hereditary 

 mechanisms. ' 



Heredity should be thought of as a general property of organisms, 

 and not as the function of a special organ of the cell or of the embryo. 

 As a phenomenon it should be associated with crystallization, on the 

 one side, and with memory, on the other. There may be simpler 

 properties of matter which render crystallization, heredity and memory 

 possible, but such properties are not yet recognized in physics and 

 chemistry, so that the terms and theories of these sciences are of little 

 use in the discussion of evolution. 



Viewed as the basis of an independent generalization the Mendelian 

 experiments ran counter to multitudes of the most obvious and best 

 established data of biology, and it may have been on this account that 

 they were so long disregarded. The apparent conflict is here ex- 

 plained as due to erroneous theories of evolution; the recognition of 

 spontaneous organic motion enables Mendel's facts to find a place in 

 the evolutionary series, and renders the general inferences of de Vries, 

 Bateson and Wilson unnecessary. Nor need the present view be 

 thought to depreciate the importance of Mendel's laws, since such dis- 

 coveries are of much greater practical value after they have found their 

 true place among related facts than while as novelties they are per- 

 mitted to obscure all the adjoining fields of investigation. 



* See ' A Kinetic Theory of Evolution,' Science, N. S., 13: 969, June 21, 1901. 



