80 CALIFORNIA ACADEMY OF SCIENCES. 



5. Abridged or shnplified transmission. In embryonic 

 development the organism does not pass through all 

 ancestral stages, but omits a portion of them in order 

 more rapidly to reach a state of maturity. 



Having clearly defined my attitude in regard to the 

 non-creativeness of natural selection and the necessity 

 of qualifying it by the laws of development, structure 

 and heredity, it will in the future frequently be found 

 convenient to speak figuratively of selection as the orig- 

 inator of this or that character. Whenever a use is 

 found for any structure or peculiarity of a species it is 

 justifiable to assume that such a character has been 

 encouraged by selection or elimination, and this is a 

 most important, although not the ultimate step, in deter- 

 mining how the feature under consideration came about. 

 It is indeed the only step which can be explained in most 

 cases, the causes of the origination of anything new 

 being so intimately dependent upon the nature of the 

 organism, that comparatively little is known of them. 



Two forms of selection still remain for consideration, 

 sexual and physiological. Both have a direct and vital 

 bearing upon the subject of the colors of birds; for if 

 sexual selection be a valid factor in evolution it is 

 undoubtedly an agent in the production of the bright 

 plumage and gay ornamentation of male birds; while if 

 the hypothesis of physiological selection be correct much 

 light is thrown upon specific color marks which would 

 otherwise appear useless. It thus becomes important to 

 consider both of these theories with considerable care. 



SEXUAL SELECTION. 



Darwin originated the theory of sexual selection and 

 Wallace has been his most determined opponent. Both 

 should be heard from before a decision is reached. 

 Darwin says;'^ " This form of selection depends, not on 



* Origiu of Species. I, p. 108. 



