PjRESIDENT 8 ADDKESS. 29 



production of experimental proof that such inheritance takes place, which 

 has never been produced, but on Weismann's part by a demonstration 

 that the reproductive cells of organisms are developed and set aside 

 from the rest of the tissues at so early a period that it is extremely 

 improbable that changes brought about in those other tissues by un- 

 accustomed incident forces can be communicated to the germ-cells so as 

 to make their appearance in the offspring by heredity. Apart from this, 

 I have drawn attention to the fact that Lamarck's first and second laws 

 (as he terms them) of heredity are contradictory the one of the other, and 

 therefore may be dismissed. In 1894 I wrote : — 



' Normal conditions of environment have for many thousands of 

 generations moulded the individuals of a given species of organism, and 

 determined as each individual developed and grew " responsive "quantities 

 in its parts (characters) ; yet, as Lamarck tells us, and as we know, 

 there is in every individual born a potentiality which has not been 

 extinguished. Change the normal conditions of the species in the case 

 of a young individual taken to-day from the site where for thousands of 

 generations its ancestors have responded in a perfectly defined way to the 

 normal and defined conditions of environment ; reduce the daily or the 

 .seasonal amount of solar radiation to which the individual is exposed ; or 

 remove the aqueous vapour from the atmosphere ; or alter the chemical 

 composition of the pabulum accessible ; or force the individual to pre- 

 viously unaccustomed muscular effort or to new pressures and strains ; 

 and (as Lamarck bids us observe), in spite of all the long-continued 

 response to the earlier normal specific conditions, the innate congenital 

 potentiality shows itself. The individual under the new quantities of 

 environing agencies shows new responsive quantities in those parts of its 

 structure concerned, new or acquired characters. 



'So far, so good. What Lamarck next asks us to accept, as his 

 " second law," seems not only to lack the support of experimental proof, 

 but to be inconsistent with what has just preceded it. The new character 

 which is ex hypothesi, as was the old character (length, breadth, weight of 

 a part) which it has replaced — a response to environment, a particular 

 moulding or manipulation by incident forces of the potential congenital 

 quality of the race — is, according to Lamarck, all of a sudden raised to 

 extraordinary powers. The new or freshly acquired character is declared 

 by Lamarck and his adherents to be capable of transmission by genera- 

 tion ; that is to say, it alters the potential character of the species. It is 

 no longer a merely responsive or reactive character, determined quantita- 

 tively by quantitative conditions of the environment, but becomes fixed 

 and incorporated in the potential of the race, so as to persist when other 

 quantitative external conditions are substituted for those which originally 

 determined it. In opposition to Lamarck, one jnust urge, in the first 

 place, that this thing has never been shown experimentally to occur ; and 

 in the second place, that there is no ground for holding its occuri-ence to 

 be probable, but, on the contrary, strong reason for holding it to be 



