General Considerations. xxiii 



senting to our minds the knowledge we possess at the passing 

 moment in a form which gives it compactness as to the past and 

 availahiHty for use in the future, that is all which in the nature of 

 the case they should be regarded as doing, or expected to do, for 

 us. An increase in our knowledge may confirm, but it may, on 

 the other hand, overthrow the most perfectly symmetrical of 

 systems ^. 



K It is not a little instructive to note that Macleay, to whom Zoology is indebted 

 for the 'grand principle' referred to above, should yet have been the inventor of 

 the 'quinary system,' with its independent but numerically identical groups arranged 

 in circular series. For the history and for illustrations of the working of this idolon 

 theatri, see Macleay, Horae Entomologicae, vol. i., pt. ii., p. 322, 1821 ; Swainson, 

 Geography and Classification of Animals, p. 202, et passim, 1835; Edward Forbes, 

 Starfishes, p. xvi. 1841 ; Milne Edwards, Ann. Sci. Nat., Ser. iii., tom. i., p. 79, 

 1844; Agassiz, Essay on Classification, p. 344, 1859. Bacon's words are singularly 

 appropriate in relation to these arbitrary assumptions : — ' Intellectus humanus ex pro- 

 prietate sua facile supponit majorem ordinem et equalitatem in rebus quam invenit ; 

 et quum multa sint in natura monodica, et plena imparitatis, tamen affingit parallela 

 et correspondentia et relativa quae non sunt. Hinc commenta ilia in coelestibus 

 omnia moveri per circulos perfectos.' Nov. Organ, xlv. Neither are the words 

 of the modern poet quoted by Sir John Richardson (Introduction, Fishes, Museum 

 Natural History), in relation to a recent attempt to unite Fishes, Amphibia, and 

 Reptiles into one division, the Haematocrya, unworthy of being quoted here :— 



' Our little systems have their day, 

 They have their day and cease to be. 

 They are but broken lights of Thee, 

 And Thou, O Lord, art more than they.' 



Tennyson, In Memoriam, vi. 



Striking evidence is borne to the scientific fact of the great difference which exists 

 between the works which are and those which are not of man's creating, by the 

 singular circumstance that of all the many metaphors which have been used to 

 express the general or picturesque efiect produced on the mind by the study of a 

 system of biological classification, those only retain a strong hold upon the imagination 

 which are borrowed from natural objects ; whilst those which are borrowed from 

 works of art, or from productions of the arts, are at once felt to be inadequate even 

 when not untrue. In illustration of this, it is sufficient to lay specimens of the two 

 kinds of metaphor mentally alongside of each other. In the 'atter we have the 

 divisions of the organic world compared to the steps in upward-sloping stairs ; or to a 

 series of columns placed upon a flight of such stairs ; or to the meshes of a net ; or to 

 the artificial boundary-lines of neighbouring kingdoms ; the more modern and truer 

 comp.arisons we refer to are drawn from such objects as single stars, each surrounded 

 with its own proper atmosphere ; as aggregations of such stars in constellations ; as 

 trees with stems, branches, twigs and leaves ; as hills clothed with woods, and sepa- 

 rated by valleys dipping to various depths, and themselves bestudded with clumps 



