254 Te. L AACO RAS ET: LocroBER 
system of “trial and error” (Huxley); (3) The reaction of the germ- 
plasm to external stimuli, ze. 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 cn, 
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 

