ARCHDALL REID ON HEREDITY 7 



is admitted on all hands that inborn traits (including varia- 

 tions) tend to descend from parents to offspring, and to more 

 remote descendants, it is now denied by the vast majority of 

 biologists that ' modifications ' (or ' acquirements ') are ever 

 inherited. . . . The whole problem of heredity centres round 

 this question of the causation of variations. It lies at the 

 starting-point of every conceivable doctrine of evolution. . . . 

 Early in the last century the philosopher Lamarck pub- 

 lished a theory of evolution which assumes in effect that all 

 variations are due to the transmission of acquirements. His 

 modern followers,- a dwindling body, assume that some varia- 

 tions arise thus. Darwin started where the Neo-Lamarckians 

 leave off. He assumed that, while many variations arise 

 apart from the transmission of acquirements, some variations 

 arise in consequence of their transmission. His modern 

 followers, the Neo-Darwinians, who include the great majority 

 of biologists, go a step further. They assume that no acquire- 

 ments are transmissible, and therefore, that none of the 

 variations of the child are due to the inheritance of parental 

 modifications. . . . When dealing with problems of heredity 

 we must always bear in mind that germ-plasm, not the indi- 

 vidual, is the real subject of discussion. The germ-plasm 

 undergoes gradual changes ; the individual enables us to 

 ascertain and indicate those changes. ... It is probable that 

 there is continuity of the germ-plasm, and therefore that the 

 individual is nothing more than an incident in its career, a 

 dwelling-place where shelter and nutrition are obtained. All 

 evolution consists, in essence, of a gradual change in the 

 character of the germ-plasm contained in successive germ-cells 

 a change of such a nature that it is reflected in the succes- 

 sive individuals that spring from the cells." 



" The Theory of Natural Selection as propounded by 

 Darwin is not a theory of heredity, but one of evolution 

 only. As a doctrine of heredity he propounded the hypo- 

 thesis of Pangenesis. But the two do not stand or fall 

 together. On the contrary, Pangenesis, since it implies the 

 transmission of acquirements, is distinctly incompatible with 

 Natural Selection, and is, moreover, quite irreconcilable with 

 the facts of modern embryology. His modern followers have 

 accepted Natural Selection while they have rejected Pan- 

 genesis, as they have the Lamarckian and Bathmic doctrines 

 of heredity. 1 Instead they have propounded several theories 



1 "The Bathmic theory supposes that evolution has occurred in 

 obedience to, and under the immediate direction of, a Deity, who has 

 rejected both natural selection and the transmission of acquirements as 

 means to His ends." 



