254 F. F- LICORISH [october 



system of " trial and error" (Huxley); (3) The reaction of the germ- 

 plasm to external stimuli, i.e. the reaction of the developing organism 

 to the external environment (Weismann). 



Let us now turn to the Neo-Lamarckians. The basis of their 

 theory is that the influences of the environment modify the organism 

 not only during the time it is being built up, but also for an indefinite 

 period after, assuredly during the time it is reaching its maturity 

 or full growth, that such modifying reactions are heritable, and that on 

 these influences the progress of evolution is chiefly dependent. As a 

 result of limiting inheritance to the reactions of the environing 

 influences during the pre-natal period, Neo-Darwinians have to call to 

 their aid natural selection, whereas the Neo-Lamarckians, by extending 

 the period of inheritance of environmental and functional reaction to 

 maturity of the organism, can dispense to some extent with natural 

 selection, believing as they do that the experiences of the organisms 

 from inception of life to maturity are conserved by heredity, and that 

 adaptation results in most cases through inheritance of those ex- 

 periences. As to the strict Lamarckian, he sees no need of natural 

 selection, believing that somatic experience is the sole cause of 

 adaptation. 



Weismann, in addition to his theory of pre-natal influence as a 

 cause of variation, has elaborated the theory that the organism is built 

 up and comes to maturity because the germ-plasm, during the building 

 up of the organism, becomes distributed through it, so as to form 

 Anlagen which are capable of developing the necessary characters and 

 of providing for lost parts, etc. It is this feature of his work as a 

 biologist that has made him a distinctive force in the science. And 

 although at first he maintained that the germ-plasm as present in the 

 germinal cells is unchangeable, more recently he has modified his 

 position, now maintaining, as already stated, that it can react to 

 external stimuli, and hence be changed by the influences of the 

 environment, — an admission of the utmost importance in the re- 

 adjustment of apparently conflicting theories. We wish to suggest an 

 interpretation of the Lamarckian theory that may bring about a still 

 closer approximation. 



It must be acknowledged by all who make a careful study of the 

 nervous system in its relation to evolution, and in its influence on 

 the organism, that it is through it that all functions are carried on, 

 and through its regulation that lost parts are renewed and injuries. 

 repaired. Moreover, it is through the nervous system, presumably as 

 germ-plasm as well as an organised portion in the ontogeny, that all 

 experiences acting thereon are registered and transmitted to the off- 

 spring. It has always been a surprise to me that biologists, in con- 

 sidering the factors of organic evolution, should have paid so little 

 attention to the influence of the nervous system in vital processes ;. 

 preferring, it would seem to me, to invest the cells themselves with 



