28 REPORT — 1000. 



subject by the genius of Charles Darwin, who formulated the wide- 

 reaching theory that variations could be transmitted by heredity to 

 younger generations. In this manner he conceived new characters would 

 arise, accumulate, and be perjaetuated, which would in the course of time 

 assume specific importance. New species might thus be evolved out of 

 organisms originally distinct from them, and their specific characters would 

 in turn be transmitted to their descendants. By a continuance of this pro- 

 cess new species would multiply in many directions, until at length from one 

 or more originally simple forms the earth would become peopled by the 

 infinite varieties of plant and animal organisms which have in past ages 

 inhabited, or do at present inhabit, our globe. The Darwinian theory may 

 therefore be defined as Heredity modified and influenced by Variability. 

 It assumes that there is an heredity quality in the egg which, if we take 

 the common fowl for an example, shall continue to produce similar fowls. 

 Under conditions, of which we are ignorant, which occasion molecular 

 changes in the cells and tissues of the developing egg, variations might 

 arise, in the first instance probably slight, but becoming intensified in 

 successive generations, until at length the descendants would have lost 

 the characters of the fowl and have become another species. No 

 precise estimate has been arrived at, and indeed one does not see how it is 

 possible to obtain it, of the length of years which might be required to 

 convert a variation, capable of being transmitted, into a new and definite 

 specific character. 



The circumstances which, according to the Darwinian theory, deter- 

 mined the perpetuation by hereditary transmission of a variety and its 

 assumption of a specific character depended, it was argued, on whether it 

 possessed such properties as enabled the plant or animal in which it 

 appeared to adapt itself more readily to its environment, i.e. to the 

 surrounding conditions. If it were to be of use the organism in so far 

 became better adapted to hold its own in the struggle for existence with 

 its fellows and with the forces of nature operating on it. Through 

 the accumulation of useful characters the specific variety was perpetuated 

 by natural selection so long as the conditions were favourable for its 

 existence, and it survived as being the best fitted to live. In the study 

 of the transmission of variations which may arise in the course of develop- 

 ment it should not be too exclusively thought that only those variations 

 are likely to be preserved which can be of service during the life of the 

 individual, or in the perpetuation of the species, and possibly available for 

 the evolution of new species. It should also be kept in mind that 

 morphological characters can be transmitted by hereditary descent, 

 which, though doubtless of service in some bygone ancestor, are in 

 the new conditions of life of the species of no physiological value. 

 Our knowledge of the structural and functional modifications to be 

 found in the human body, in connection with abnormalities and with 

 tendencies or predisposition to diseases of various kinds, teaches us that 



