258 lotsy's theory of evolution. 



De \"ries' mutation theory, and in both theories the theory of 

 natural selection is required, at all events as a subsidiary 

 theory. Darwin tried to get an idea how external influences 

 may cause variations by means of his " formal " theory of 

 pangenesis, while De Vries, objecting to the direct influence 

 of external circumstances, tried to explain variation by his 

 theory of intra-cellular pangenesis." During recent years the 

 question of the origin of species has been brought into a new 

 path by the re-discovery of Mendel's laws, which fitted in with 

 many of Weismann's speculations, and also with De Vries' 

 theory of pangenesis. Thus, in his very first publication on 

 Alendelism, " Das Spaltungsgesctz der Bastarde " ( Vorlaitfige 

 Mitthciluncj), De Vries states at the beginning:* 



According' to pangenesis, the whole character of a plant is composed 

 of definite units. These so-called elements of the species or elementary 

 characters are imagined to be connected with material bearers. There 

 are no transitions between these elements, just as little as there are none 

 between the molecules of chemistry. 



It seems that this view can hardly be maintained any longer. 

 Thus Bateson states :t 



Some of my Alendelian colleagues have spoken of genetic factors as 

 permanent and indestructible. Relative permanence in a sense thev have, 

 for they commonly come out unchanged after segregation. But I am 

 satisfied that they may occasionally undergo a quantitative disintegration. 



But if I understand this rightly, it means that they may dis- 

 appear altogether, and such characters as, e.g., hairiness and 

 smoothness of plants, will pass into one another, and natural 

 selection will have to come in not only with these characters, 

 but also with correlated characters. t Bateson does not specu- 

 late on the evolution of species. 



The thought uppermost in his mind is that knowledge of the nature 

 of life is too slender to warrant speculation on these fundamental 

 subjects. 



But the sentences which I have quoted above seem to me to 

 >ho\\ L'iat lie overstates the case when he tcU^ usc' that 



Jordan was perfectly right. The true breeding form which he dis- 



tinguished in such multitudes iire real entities, though the great system- 

 atists dispensing witii them have pooled them into arbitrary Linnean 

 species for the convenience of collectors and for the simplification of 

 catalogues. 



On the same page he says : 



Lotsy has lately with great courage suggested to us that all varia- 

 tion may be due to crossing. || I do not disguise my sympathy with this 



■' Ber. der deutsch. hot. Grs. (1900), S3. 



tRept. Brit. Assn. for Adv. of Sc, Australia (1914). t6. 



t For instance, in certain species of Cotyledon, as in C. orbieulata L. 

 the nectar chamber is closed by tufts of hairs on the filaments, in others 

 closely allied in all other characters as, e.g., in C. vcliitiua Hook f. the 

 hairs are gone, but the filaments are broadened at the base, and perform 

 the same function. 



§ Op. cit. 15. 



il Lotsy states plainly that Kerner was the first to su.ggest that new 

 species arise through crossing, and he shows how far his conceptions 

 differ from those of Kerner. ■ 



