256 Mr.W. S. MacLeay om certain geiieral Laics regulating 



indicat ; perfectissima enim sunt in qiiavis sectione ab omnibus 

 aliis remotissima. Sic perfectissima animalia et vegetabilia, 

 quaj maxime a se invicem remota; infima, quorum limites 

 confluunt." Hence it follows, that the centrum, or perfection 

 of a rn'oup, is in fact that part of the circumference of the cir- 

 cle of affinity which is furthest from the neighbouring group, 

 and exactly the same thing with what in the Horce Entomolo- 

 giccc has perhaps more happily been called Type. 



Indeed the confusion arising from the use of the word cen- 

 trum., as applied to a point in the circumference of a circle, is 

 still increased by applying the word radii to those groups like- 

 wise in the circumference which lead from one centrum or 

 type to another, and which I have termed annectcnt groups*. 

 The use of these terms centrum and radii is the more unfor- 

 tunate, as our author never for a moment takes them in any 

 other sense than that in wliich I have used the expressions 

 type and anticctent groups. "When, therefore, he says that in 

 every group, whether class, order, &c. there are a centrum and 

 radii, we must understand him as meaning, that there are in 

 eveiy circle first a type or normal form expressing the perfec- 

 tion of the superior group to which it belongs; and secondly, 

 annectent groups connecting this type with other groups. Or, 

 to take his own words, " In centrum quod species plurimas 

 continet, character optime quadrat. Radii ad reliquas classes 

 (scilicet ordines, genera, &c.) abeuntes, utriusque classis cha- 

 racterem conciliant, sed ad illam (viz. the typical group) cujus 

 character maxime eminet referuntur." 



If then the determinate number in which Tungi are na- 

 turally grouped be four, and if it thus appears that, according 

 to M. Fries, every natural group is a circle, having in its cir- 

 cumference a point of perfection or typical group called a 

 centnun, and annectent groups called radii, it is evident that 

 there must be one centrum and three radii for every group. 

 But observe what immediately follows as the result of 

 M. Fries's observation : " Centrum abit semper in duas series, 

 inferiorem et superiorem, quarum ilia ad antecedentem hcec 

 ad sequentem classem (1. radium) evidentius accedit." 



This rule being determined, M. Fries goes on moreover to 

 say, that these two series which compose the cenhnim are al- 



ledoneis esse anteponendas." p. 6. De Plantarum Classtficalhne Naturali 

 H'nquisitionihus Aiialumicis et P/it/siotogicis stabilicnda Commcntalio, Auctore 

 A. F. Sclni'cigger, Si-c. RegioimiiH 1820. 



* There are several other terrtr; used by M. Fries to designate his groups, 

 and which ditlbr from those employed by me to express the nature of simi- 

 lar groups. Thus, his iniermediate genera are my (mcntavt gniera ; his sub- 

 ordinate genera are my types of form or sub-genera, &c. 



ways 



