Notices of New Books. 7581 



relating to instinct, hybridism, the imperfection of the geological 

 record, and anomalies in geographical distribution, relate more parti- 

 cularly to the discussion of difficulties and their attempted explanation. 



With reference to those facts which Mr. Darwin considers aiford 

 him natural evidence in favour of the gradual multiplication and pro- 

 gression of organized beings : Chapter II. relates to the variability of 

 species, as observed under a state of nature, as individual differences 

 determined by peculiarities of habitat, instanced in dwarfed plants on 

 alpine summits, and the quantity and quality of fur of animals having 

 a wide range determined by temperature, and the dwarfed condition 

 of certain shells in the brackish waters of the Baltic ; also individual 

 differences under identical circumstances, as individual variations in 

 the plumage of certain birds, the want of uniformity in the muscles of 

 the individual larvae of certain insects. 



Again : the difficulties naturalists have met with in defining the 

 characters which distinguish a species from a variety he says imply 

 that they are but different degrees of the same kind of difference, and 

 that, the consanguinity between varieties and their parent species 

 being acknowledged, genealogical relationship between kindred species, 

 and again between the higher grades of classification, is fairly implied. 

 At page 53 (third edition) Mr. Darwin says, " Certainly no clear line 

 of demarcation has yet been drawn between species and sub-species, 

 i. e., the forms which in the opinion of some naturalists come very 

 near to, but do not arrive at the rank of species ; or, again, between 

 sub-species and well-marked varieties, or between lesser varieties, 

 and individual differences. These differences blend into each other in 

 an insensible series, and the series impresses the mind with an actual 

 passage." Again : that the kind of relationships existing between 

 varieties and their acknowledged parent species has, in each natural 

 series, a striking parallel resemblance to the relationship subsisting 

 between the species and the higher grades of classification ; for 

 the number of the varieties of a species is generally proportionate 

 to the size of its genus, each species of large genera having a greater 

 number of varieties than each species of small genera, exhibiting a 

 parallel relationship between the affinity of the variety to its species 

 with that of the species to its genus, implying in the resemblance 

 an inherited property : and that allied species once held the same 

 relationship to some common progenitor that varieties now do to each 

 of their acknowledged parent species. 



At page 57 (third edition) is stated, " From looking at species only 

 as strongly-marked and well-formed varieties, I was led to anticipate 



