M ERISTIC VARIATION. [ PAUT l - 



eye-spots of some Satyrid butterflies, &c., are each in themselves 

 nearly symmetrical. To these separate systems of Symmetry the 

 i, TIM 'Minor Symmetry will be applied. Minor Symmetries may 

 or may ii"t be compounded into a Major Symmetry. Between 

 tli. - there is of course no hard and fast line. 



In each .-lass of Symmetry, Meristic Repetition may occur, and 

 tip- repeated parts then stand in either 



1. Lint-ar or Successive Series. 



1 1 Bilateral or Paired Series. 



111. Radial Series. 



ts meristically repeated may thus stand in one or more 

 ,1 ivlatkms to each other, and the first part of the 



lence t M.-ristir Variation will be arranged in groups according 



i- in on,- or other of these relations that the parts are affected. 

 In each group cases affecting Major Symmetry will be given first, 

 an. I those atV.-eting Minor Symmetries will be taken after. 



A- i; i- proposed to arrange the facts of Meristic Variation in 



ipe corresponding with these three forms of Meristic Repetition, 



ill he ii.-.-t'ul to consider briefly the nature of the relation in 



which the members of such series stand to each other, and the 



.liaia.-t.-r- distinguishing the several kinds of series. Reduced to 



th.- -impl- -t terms, the distinction may be thus expressed. 



In tin Liii'-ar or Successive series the adjacent parts of tint/ 

 (,!>.. nn-ii tbers of the series are not homologous, but the 



/-///// liniimlniiniis parts of each member or segment form a 

 .iltfi-iKitinff with each other. For example, the 

 anti-ri'T and posterior -ur faces of such a series of segments may 

 he n-pr. -. -nt.-d 1'V th.- .-.TICS 



J ,AP,AP,AP, P. 



'I'll.- relation of an\ jiair .if organs in Bilateral Symmetry differs 

 tV"in thi-. for in that case ""/< ///>'////-/ of the pair presents to its 



I'l'llnir <//' ///c i.yv"'"'' 1 x '"''' /""'''>' liiii<iluiji>iiK //'it/I those which its 



/'//.,// y/rr.N-/(/.s- in it. <"ir/, l,,in;l, in xt rurf H fC it ml position, an 



ujttii-nl mi'i'K "f t/ir "flier. Tht- rxtt-rnal and internal surfaces of 

 >in-h a pair may tht.-ivti>iv In- i-rjirrM-nti-d thus: 



/: /. i K. 



If tin- maniit-r !' origin of tlu-s<- two kinds of Repetition be 

 considered, il \\ill !< seen that though both result from a process 



I' I >i\ ision, yet the niann.-r of l>i\ision in the two cases is verv 



ditVi-n-nt. F..I- in tin- case of division to form a paired st nu-t lire, 



tip- pi OCCUn in >urh a way a- to t'"rin ;1 pair of images, 



ot uhidi similar and homologous parts ]j,. ,,n r aeh side of the 



plane of division ; \\hile.in the toi-mation ..('a chain of successive 



ments, each |>lane .f divi-ion pa^-es li.-tween parts which are 



dis-iiiiilar, and \\h>>e !ioinol.gy is alternate. The distinction 



11 the-e tw.i kinds of l)i\ivion is of course an expression of 



the ta.-t that the at t raet ioi,s and repnUion> from which Division 



