IQ-fc Mr. W. S. MacLeay on certain general Laics regnlatiug 



solely in observation, and wliicli, if properly followed up, will 

 infallibly induce us to grant to Bonnet the truth of his pro- 

 position, that affinities are continuous, and yet to agree willi 

 his opponents that the series of natural beings is not simple. 

 This rule is, that Briations of Analog}] mu%t he carrfuUi/ distin- 

 guished J)om llelations qfjjfinilij; lor, as our author M. Fries 

 most truly says, " Qjio magis in snpeijicie acqnieverunt naturce 

 scrutalores, eo magis analnga cum afjinihus commuturunt." 



The ideas of Affinity and Analogy are so distinct from each 

 other in the mind of every person acquainted with the first 

 principles of logic, that even while this distinction was not laid 

 down as an axiom in natural history, experienced naturalists 

 perceived that every correspondence of character did not ne- 

 cessarily constitute an affinity. Thus the celebrated Pallas, in 

 his Elenchus ZoopJiytorum, has well-observed that Bonnet, in or- 

 der to complete his linear scale of nature, was obliged to aban- 

 don the true vinculum of affinity, and to resort to such super- 

 iicial or analogous characters as those which connect Vesper- 

 tilio and E.vocectus with birds. But the nature of the diffijrence 

 which exists in natural history between affinity and analogy, 

 was I believe first discovered in studying Lameliicorn insects ; 

 and in the year 1819, when I published that discovery*, the 

 fifth part of an acute jihilosophical work, entitled Botanical 

 Aphorismsf , appeared in Sweden, wherein the distinguished 

 cryptogamist M. Agaiuh proves by the following words, that 

 lie likewise had a sliglit glimpse of the same truth : " Analogia 

 (jUffidam et similitudo in diversis seriebus vegetabilium inter- 

 duni cernatur, quasi progressa esset natura ad perfectionem 

 per eosdem gradus sed diversa via J." 



* The 1st Part o? Hone Entonwlogiae is here alhided to. — Edit. 



f Aphorismi Botanici, qiios veniri Ainpliss. Orel. Philos. Lund. Praeside 

 C.irolo Ad. Agardh, &c. pro Gradu Philosophico, p.p. N. Kuhlgren,&c. p. v. 

 Lnnda;, 1819. 



J In the same little tract M. Agardh makes two other observations, which 

 cjincide with what I have noticed in the animal kingdom. The first is as 

 follows : " Inter inlVriores formas superiores sa;pe efflorescnnt, sed riides et 

 veluti experimenta : sic anticipationes t'ormae perfection's in plantis inferio- 

 ribus non raro obveniant ; lit etiam in plantis supcrioribus regressiis ad 

 formam imperfectiorem." Now in the Iloiee linfomologicce, p. 223, 1 have 

 attempted to show that Nature, in the imperfectly constructed Acriia, 

 sketches out in a manner the five principal forms of the animal kingdom. 

 So also the direct return of Annulose Vermes to Acrita is repeatedly as- 

 serted in the same work : this however seems to depend moi'e properly on 

 M. Agardh's other observation, viz. " Duplex est itaque affinitas plan- 

 tarum, aut ea, qucC oritur e transitu ab una forma norniali ad alteram, aut 

 ca, quae versatur imprimis in anticipatione formac superioris aut regressu 

 in formam inferioreni. Illam affinitatem tramitits appellamus, banc trmi- 

 niiltationis." Tiiis affinity o\' transultation is evidently nothing else than the 

 dlsjjosition observable in opposite points of the same series or transHus of 

 nflinity to meet each other, and of which I have given various examples in 



tlu- Hurce Eidunioldoico', p. 319. t^, 



■^ ' ' 1 he 



