FIELD AND FOREST. 99 



poles. The inference is irresistible that such types have migrated 

 from common ground, and may have originally developed either in 

 the deep sea and thence dispersed in opposite directions, or at one of 

 the extremes and wandered thence over the bottom to their final rest- 

 ing places. However this may be, a primary combination of the ma- 

 rine faunas is most natural under the categories of tropicalian, arc- 

 talian, and notalian, while the temperate ones are rather the com- 

 plexes of the bounding regions. 



It is impossible within the limits of a review to discuss the numerous 

 questions raised in Mr. Wallace's work, or to notice errors cf detail. 

 Numerous as are the subjects discussed, many of equal importance 

 are scarcely, if at all, noticed. Such are the correlations between 

 developement in size, as a whole and in different parts, and longitude 

 and latitude ; the correlation of color with surface of country ; and the 

 connection of physiological modifications and habitat. We have to 

 say, too, that the errors in detail are extremely numerous, and are 

 sometimes the results of imperfect information per se, and sometimes 

 of misunderstanding of the authorities consulted. Some of these er- 

 rors are very grave. Thus, Mr. Wallace informs us that " the opercu- 

 lars of the globe are about one-seventh, the inoperculata about six- 

 sevenths of the whole " of the terrestial gastropods ; " but when we 

 come to the Antilles we find them to amount to nearly five-sixths, 

 about half the operculata of the globe being found there ! " (vol. ii. 

 p. 527 ; the exclamation mark is Mr. Wallace's own). The truth is 

 that in the Antilles the operculate species are, as elsewhere (although 

 in a much less degree), very much less numerous than the inopercu- 

 late, there being, according to Mr. Bland in 1866 (whom Mr. Wal- 

 lace quotes), only 603 operculate to 737 inoperculate species. How 

 Mr. Wallace happened to make such an astounding blunder it is diffi- 

 cult to conceive. But we add with pleasure that even this error is to 

 a considerable extent atoned for by the judicious remarks on princi- 

 ples of distribution which immediately follow. The want of familiar 

 knowledge of the different classes treated of, and consequently of im- 

 mediate and instinctive availability of the facts, has often prevented 

 the author from following the facts to their logical results. Mr. Wal- 

 lace's aim was a lofty and laudable one, viz. : " that this book should 

 bear a similar relation to the eleventh and twelfth chapters of the 

 ' Origin of Species ' as Mr. Darwin's ' Animals and Plants under Do- 



