384 BihUograpMcal Notice. 



with the central form, which is numerically far their inferior and 

 very restricted in its range. The differences developed in this local 

 central form during the period of Isolation are being slowly absorbed 

 by Interbreeding, now that the Isolation has ceased ; and the race 

 which would probably have firmly established itself and spread east 

 and west, had it not encountered on either hand a bar to its pro- 

 gress in the two more flourishing, stronger, and wider-ranging forms, 

 is being worsted in the struggle with them, and is slowly but surely 

 passing away." It is easy to see that there are weak points in this 

 argument, but the facts are in themselves interesting and seem to 

 open up a line of inquiry which may lead to most valuable results. 



In the earlier part of this notice we have felt compelled to dissent 

 from the interpretation put by Mr. Dixon upon the now classical 

 term " Natural Selection," and to indicate that, while he is free 

 from that semi-superstitious veneration for it which seems to lead 

 many enthusiastic disciples of Mr. Darwin to regard the phrase as 

 something akin to the unintelligible words employed by the sorcerers 

 of former days to banish demons into the Ked Sea or a hotter 

 locality, and as serving to settle all matters in dispute and consign 

 their opponents at once to a limbo intellectually almost equally 

 disagreeable, he has himself made a mistake in the opposite direc- 

 tion, and thus been led to undervalue the theory established by the 

 greatest naturalist of our day. The fact appears to be that the 

 author has altogether misunderstood the sense in which Darwin 

 employed the word " Selection." Thus he says (p. 54), " Sexual 

 Selection does not depend on taste alone, although it may seem a 

 misnomer to so entitle such a means of modification if clioice is not 

 the exclusive agent employed ;" but we find a glimmer of better 

 things in the statement, that " the term Sexual Selection is so well 

 known that it would be unwise to change it ; but it must always 

 be borne in mind that it is used in a very broad sense,"— that is, we 

 presume, in a sense consistent with the general theory of Natural 

 Selection. Nevertheless he has just previously stated that " Darwin 

 placed too much confidence in Natural Selection and far too little 

 in Sexual Selection." 



But in the various sections of his book, in which he bases his 

 arguments exclusively upon ornithological data, he has brought 

 together a mass of most valuable detailed observations upon the 

 variations of birds in connexion with their geographical distribution, 

 and his remarks upon these will be found very interesting and valu- 

 able for the student of ornithology. At present, when the idea of 

 absolute fixity of species has been given up by almost all naturalists, 

 the question of the claims of particular forms to specific rank has 

 become one of great difiiculty ; and every contribution, such as this 

 little book affords, towards the unravelling of the web of doubts and 

 queries in which the feet of the student of systematic zoology and 

 of the range of species are entangled at every step must be welcome. 

 From this point of view we can conscientiously recommend Mr. 

 Dixon's book to the notice of his fellow workers. 



