Vol.X-| Recent Literature. *9* 



1S93- J 



same diversity of opinion prevails, one school advocating sexual selection 

 as the sole agent in producing the brilliant colors and varied plumes of 

 male birds, etc., the other extreme asserting that sexual selection as a 

 factor in evolution is a myth. Still greater is the diversity of opinion 

 and more intense the feeling in regard to that momentous question which 

 is at present agitating the troubled sea of scientific thought-the trans- 

 mission of acquired characters." 



Concerning all of these leading questions Mr. Keeler spreads before his 

 readers the pros and cons of the argument as presented by leading cham- 

 pions giving a concise history and impartial summary of the contesting 

 theories Mr. Keeler also now and then attempts to weigh the evidence 

 brou-ht forward by the different opposing advocates, but for the most 

 part maintains a position of neutrality or judicial reserve to such an ex- 

 tent that it is sometimes difficult to see which side of the case he favors, 

 till we reach his final summing up of the subject. 



In discussing the inheritance of acquired characters he appears to allow 

 great weight to the supposed distinction between the inheritance of a 

 habit or the modification of a structure and the inheritance merely of a 

 "constitutional tendency" to a given habit or to a given vanation-a 

 distinction we confess too occult for our comprehension. At the close of 

 his discussion of heredity he says: "From all this we may come to a 

 provisional conclusion that acquired characters are transmissible. We 

 are justified in using this assumption as a working hypothesis, and in 

 feelin- confident that future investigation will place it upon a footing 

 whereit is beyond the possibility of refutation." For this concession we 



are duly grateful ! 



Mr Keeler admits himself to be a strong convert to the theory of sexual 



selection as he interprets it, and that it affords "a tolerably complete 

 explanation of secondary sexual characters in birds," after considering the 

 evidence pro and con, at considerable length. We are quite unable, 

 however to see the evidence as it appears to him; or at least to accept 

 the principle of sexual selection as he applies it in the second part of his 

 work- in other words, that the secondary sexual characters among 

 birds' or among any other animals, are due to any great extent to volun- 

 tary' selection on the part of the female. The subject is of course too 

 broad to admit of discussion in the present connection. 



Mr Keeler, we are glad to see, gives the cold shoulder to Mr. 

 Romanes's rather baseless theory of 'Physiological Selection,' which has 

 already received many well-merited thrusts, since it is primarily based 

 upon an assumption not only impossible to prove in the slightest degree, 

 but at the same time seemingly of the utmost improbability. 



In the two hundred and odd pages devoted to 'The Colors of North 

 American Birds' there is much that is suggestive and worthy of commen- 

 dation mixed with a great deal that is weak and unphilosoph.cal, which 

 on the whole leaves a feeling of regret and disappointment, when com- 

 pared with the able presentation of the subjects treated in the first third of 



