84 Heredity, Variation and Genius 



it apparently does in the rabbit, the mouse, and 

 the horse ; besides which, there is some reason 

 to think that cases of blending in animals do 

 actually occur.* 



Whatever the ultimate value of these rules may 

 prove to be, it would be unreasonable to expect 

 yet to apply them to man, seeing how recent was 

 the recognition of them and how numerous and 

 various are the complications in the matter of so 

 complex an organic being. A character which 

 looks simple and suitable to be treated as a unit 

 may not be simple at all — most likely is not — but 

 subtilely composite and dependent upon the in- 

 tricate interactions of various factors separately or 

 not transmitted in heredity. All the more reason 

 to think so seeing that the particular colour even 

 of rabbit or mouse seems not to be a simple 

 factor but to depend on interaction between one 

 distinct factor and another which are separately 

 transmitted. 



Evidently the special need now is of a systematic 

 observation and exact record of the facts of human 

 heredity in place of the vague and general state- 

 ments hitherto put forth without the least profit. 

 A painstaking and thorough investigation of the 

 lineage of a single family and its adventures, 

 accurate note being taken not of the cases only 

 in which a particular transmission occurs and is 



* An Address on Mendelian Heredity and its Application 

 to Man. W. Bateson, M.A., F.R.S., British Medical Journal, 

 July 14th, 1906. 



