Presidential Address. 7 



in their helping to do away with the intercrossing bogey in regard to Natural 

 Selection ; and (2) in their remarkable support which they appear to give to 

 the idea of localisation of hereditary characters within the gametic chromatin 

 as suggested long ago by Weismann. 



Superficiality of Biological Knowledge. 

 I should like to accentuate the necessity of constantly bearing in mind 

 how extraordinarily superficial our knowledge is of many of the characters of 

 animals that we study. If we compare say a mammal from which a particular 

 organ has been removed by operation early in life, with another of the 

 same species in which there is congenital absence of the same organ, our 

 first impression is that the two individuals are alike, and we are struck with 

 surprise that the absence of the organ is inherited in the one case and not in 

 the other. As a matter of fact there is a profound difference between the 

 individuals. The congenital absence or presence of an organ is a superficial 

 symptom of a profound difference in the constitution of the animal. When 

 we remove the organ by operation, we remove only that superficial character 

 without touching the extreme complexities of constitution of which its 

 presence is the expression. Can we wonder then that the deep-seated 

 characters are inherited and the superficial not ? It appears to me that the 

 failure so far to substantiate the inheritance of acquired characters may be 

 due simply to the superficiality of the characters which have been specially 

 investigated. If this be so, then what we have to do is to cause characters 

 to be acquired in response to some induced change in constitution, and we 

 may well expect such to be inherited. 



Classification of Variations. 



Variations are obviously to a certain extent reactions to environmental 

 conditions — such are "acquired" characters, e.g., the variations which are 

 brought about by causing zygotes of the same ancestry to develop under 

 different sets of environmental conditions. It seems, by the way, remarkable 

 how comparatively little attention has been paid to this field of investigation. 

 Surely one of the first essentials in a scientific investigation of variation is 

 to endeavour to get our notions clearer as to the relative importance of such 

 characters in building up the complex of features characteristic of the 

 individual. Behind this problem of the effect of external conditions upon 

 the zygote or individual, lies the still more important problem of the effects 

 of such conditions upon the gametes — or better gonad — during the period 

 before the occurrence of the karyogamous formation of the zygote. 



I cannot help feeling that if we were able to get at them, we should find 

 that the characters which exist in an invisible form in the gamete are — like 



