ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 431 



But such variations do not alter the type, e. g. the horse, whose races 

 persist and do not run into each other, but are nevertheless known 

 to be of common origin. 



With regard to species, two kinds must be distinguished : " There 

 are primordial species, that is to say, species whose origin cannot be 

 attributed by the method of analogy to ancestors of another organic 

 form, whose type has no other representative in the present condition 

 of things ; but there may also exist derived or secondary species, that is 

 to say, races of individuals which remain distinct from each other, 

 and are characterized by invariable structural peculiarities, but which 

 differ so little from one another that one is right in regarding them 

 as sprung from one identical stock." The latter are also here called 

 permanent races, and the secretary-bird, the giraffe, and man, are 

 given as instances of the first case, many so-called species in the 

 pigeon and dog genera are cited for the second, as being of no greater 

 specific importance than local varieties. The author considers that, 

 on the one hand, writers who have looked on all species as pri- 

 mevally established, have multiplied species to an inadmissible extent, 

 simply on the ground of the differences seen to exist between them at 

 present, no account having been taken of the unequal capacity for 

 variation exhibited by different forms ; while their opponents have 

 exaggerated the importance of the principles under which species 

 vary, and have thus drawn unauthorized conclusions as to the origin 

 of the present state of the animal kingdom. 



A most important principle is that the older a race is, the less 

 it has been mixed v/ith other races; and the less alteration of locality 

 it has undergone, the more stable are its characters. For species 

 as well as races must have had their beginning, and they have their 

 periods of youth and mature age ; they appear by analogy to be 

 modifiable in different degrees ; and thus one exposed to various 

 influences in its early stage would vary when an older and more fixed 

 type would remain constant. Thus a species soon after its origin would, 

 if its members were scattered over different localities, give rise to 

 special races or derived species, which might, if kept in their localities, 

 become fixed and assume the condition of primordial species. 



Of causes which tend to keep races of a species distinct are men- 

 tioned, difference in size, and difference in the period of sexual 

 activity ; also any modifications undergone by accessory parts of the 

 generative apparatus, as the excitant odoriferous glands. Other modi- 

 fications, such as those of the colours of the tegumentary system, and 

 the proportions of parts of the body, produced by altered conditions, 

 have less zoological imi^ortance, for they may vary in different indi- 

 viduals. But the varieties produced will always be more numer(jus 

 the more widely the species is distributed ; special attention, in dealing 

 with geographical zoology, must be paid to difference or similarity 

 existing between the species of the fauna under study and those 

 of other regions. 



The more special observations are entitled ' Memoir on the Fauna 

 of the Antarctic Eegion.' First Part. Preliminary Considerations 

 (noticing briefly the physical conditions of the district) ; and Second 



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