TINNEAX SOCIETY OF I.OXDOX. 89 



of physical or chemical plieiiomena of life. Yet tliese grains and 

 spores sprouled and developed to norniiil plants. I see no way of 

 explaining these facts tban by the assumption that life is the 

 result of forces working between sub^t:inces not living themselves, 

 and this is in perfect accordance with the view that the genes 

 need not be living particles, but may be, as Hagedooru suggested, 

 autocatalytic ferments. 



I can now state in a very few words the gist of my theory : — 



Xew species are born into the world as a result of a" cross 

 between already existing ones. The species born is ready 

 (finished) and stable, not subject to any liereditable variability, 

 except, possibly, occasional loss of a factor. JN'ature, consequently, 

 " facit saltum." The jump, however, may be very small ; the size 

 of the jump is not essenlial, the essential thing is that there are 

 no intermediate stages between species. 



There can be no question of the making of a species by any 

 form of selection by which certain individuals belonging to the 

 species to be transmuted are favoured above others, because the 

 bestowal of such favour could have no elFect, as all individuals 

 belonging to one species are identical so far as inheritable qualities 

 are concerned. 



Or, in very few w^ords, intraspecific selection is impossible. 



Interspecific selection remains possible. "Whether it occurs or 

 not, depends on the fact whether extermination goes on indis- 

 criminately or whether in all — or, at least, in the majority of 

 cases — the best species are selected. 



This problem is a very vast one ; without a minute knowledge 

 of the struggle for life in a particular case it seems to me 

 unanswerable. Anyhow, it lies outside the pale of my subject : 

 the origin of species. 



A discussion followed : — 



Prof. W. Bateson said be was glad that Professor Lotsy had 

 brought his theory for discussioTi to a meeting of the Linnean 

 .Society, the classic ground for snch a debate. The paper should 

 lead naturalists to appreciate the difficulties besetting both the 

 theory of evolution and the practice of the systematists. "Witii 

 Professor Lotsy's main contention he had great sympathy. On 

 present knowledge the homozygous forms were the only definite 

 entities. It ^Aas true that most of the facts we had formerly 

 taken as evidence of variability must now be otherwise interpreted. 

 He 8U])posed that all who had witnessed the polymorphism of a 

 large E^ family, raised from an original cross between two very 

 distinct parents, must ha\e wondered, with Professor Lotsy, 

 whether it may not have been by such crossing that the origin of 

 species has come about. Prof. Bateson admitted that crossing was 

 the most probable origin of very many species. He held, never- 

 theless, that variation by Zos-; of factors was clearly pi-oved to be 

 a real phenomenon of genetic physiology. Whether any factor 

 could be added was doubtful. Certainly, at present, there was no 



