Pre-Mendelian JVritings 5 



as offering matter too trivial for their attention may engage 

 in genetic inquiries with great confidence that every frag- 

 ment of solid evidence thus discovered will quickly take 

 its place in the development of a coordinated structure. 



Some pre-Mendelian Writings. 



Of the contributions made during the essayist period 

 three call for notice : Weismann deserves mention for his 

 useful work in asking for the proof that *' acquired 

 characters" — or, to speak more precisely, parental ex- 

 perience — can really be transmitted to the offspring. The 

 occurrence of progressive adaptation by transmission of the 

 effects of use had seemed so natural to Darwin and his 

 contemporaries that no proof of the physiological reality 

 of the phenomenon was thought necessary. Weismann's 

 challenge revealed the utter inadequacy of the evidence 

 on which these beliefs were based. There are doubtless 

 isolated observations which may be interpreted as favouring 

 the belief in these transmissions, but such meagre indications 

 as exist are by general consent admitted to be too slight to 

 be of much assistance in the attempt to understand how the 

 more complex adaptative mechanisms arose. Nevertheless 

 it was for the purpose of elucidating them that the appeal 

 to inherited experience was made. Weismann's contribution, 

 though negative, has greatly simplified the practical invest:i- 

 gation of genetic problems. 



Though it attracted little attention at the time of its 

 appearance, an honourable place in the history of our 

 science must be accorded to the paper published by 

 de Vries (1889) under the title Intracellulare Pangenesis. 

 This essay is remarkable as a clear foreshadowing of that 

 conception of unit-characters which is destined to play so 

 large a part in the development of genetics. 



The supreme importance of an exact knowledge of 

 heredity was urged by Galton in various writings published 

 during the period of which I am speaking. He pointed 

 out that the phenomena manifested regularity, and he made 

 the first comprehensive attempt to determine the rules they 

 obey. It was through his work and influence that the 

 existence of some order pervading the facts became generally 



