ROUX : HEREDITY AND FUNCTION 323 



characters, of palingenetic from cenogenetic-- a criterion 

 which descriptive morphology was unable to find. 1 The 

 introduction of a functional moment into the concept of 

 heredity was a methodological advance of the first importance, 

 for it linked up in an understandable way the problems 

 of embryology, and indirectly of all morphology, with the 

 problem of hereditary transmission, and gave form and 

 substance to the conception of the organism as an historical 

 being. 



It is this element in Roux's theories that puts them so far 

 in advance of those of Weismann. Weismann did not really 

 tackle the big problem of the relation of form to function, 

 and he left no place in his mechanical system of preformation 

 for functional or second-period development ; he conceived 

 all development to be in Roux's sense embryonic, and due 

 to the automatic unpacking of a complex germinal organisa- 

 tion. Roux himself was to a certain extent a preformationist, 

 for the development of his first-period characters is con- 

 ditioned by the inherited organisation of the germ-plasm, 

 and is purely automatic. It was indeed his experiments on 

 the frog's egg (1888) that supplied some of the strongest 

 evidence in favour of the mosaic theory of development. 

 The number of Anlagoi which he postulates in the germ is 

 however small, and the germ-plasm in his conception of it 

 has a relatively simple structure (p. 103, 1905). 



The transmission of acquired characters forms, of course, 

 an integral part of Roux's conception of heredity and develop- 

 ment, for without this transmission second-stage characters 

 could not be transformed into first-stage characters. He 

 discusses this difficult question at some length in the 

 Kainpf der Theile> coming to the conclusion that such 

 transmission takes place in small degree and gradually, and 

 that many generations are required before a new character 

 can become hereditary. He thinks that acquired characters 

 are probably transmitted at the chemical level. It is 

 conceivable that acquired form-changes are dependent on 



1 M. Fiirbringer, perhaps under the influence of Roux, emphasised 

 the importance, from a morphological point of view, of studying post- 

 embryonic (functional) development, Unters. z. Morpk. u. Syst. der 

 Vbgel, ii., Amsterdam, p. 925, 1888. 



