_,8._THE NATURE OF HEREDITY. 



Bv Arthur Dkxdy, D.Sc. F.L.S.. Professor of Zoology in 

 THE South African College, Cape Towx. 



IXTRODUCTORY REMARKS. 



Ill response to the invitation which I have received to make 

 some ciMitribution to the proceedings of Section B of the South 

 African Association for the Advancement of Science, I venture to 

 bring before you some notes on a subject in which I have been 

 deeply interested for many years, and in which, indeed, no student 

 of nature can fail to be deeply interested. The problem of Heredity 

 is one which lies at the very root of the Biological Sciences, but so 

 difficult is it to grasp that a recent writer, entitled to speak with 

 authorit) , states " that as to the essential nature of these phenomena 

 we still know absolutely nothing."* I venture to- think, however, that 

 some suggestions at least have been made by well-known writers which 

 are of great value in helping us to^ form some conception of the true 

 nature of hereditv. More particularly I consider that the views 

 of Herbert Spencer. Cope, and Detmer, to which I shall refer 

 later on, have not received the consideration which they merit at 

 the hands of biologists, and it will be seen that the ideas, which I 

 now venture to bring under your notice are to a large extent identical 

 with those of the eminent writers mentioned. 



Ever since the publication of Danvin's theory of " Pangenesis," 

 what we mav i)erhaps be allowed to term a materialistic method of 

 explaining the phenomena of heredity and development has occupied 

 the attention of many biologists. It has been commonl\ assumed 

 that the observed facts of the transmission of characters from parent 

 to offspring can only Ije explained on the assumption that the in- 

 numerable characters which any organism exhibits are represented 

 by so manv material particles- " gemmules " of Darwin or "deter- 

 minants " of Weismann — which are stored up in the protoplasm of 

 the germ-cells, an assumption which is indeed improbable when we 

 remember the microscopic size of the cells in question and the 

 number of characters which have to be taken into account, and 

 which seems quite unnecessary when we remember how physical 

 forces are known to act upon objects at a distance without the inter- 

 vention of any material substance whatever. The well-known pheno- 

 mena of magnetism and electrical induction, and especiallv .such 

 modern discoveries as that of wireless telegraphv. should alone be 

 sufficient to put as on our guard against accepting as necessar\^ any 

 theor\- which assumes the existence of such inconceivably complex 



'■' Bateson. " ^k-nck-r^^ I'linciplcs of Heredity." p. 3. 



