1823.] the mtural Distribution of JjmQU and Fungi* 32? 



Ill the same year (1821) likewise appeared the abovemen- 

 tioned work of M. Fries on Fungif which is explicit ou the sub-r 

 ject, and wherein the very same expressions of affinity and ana- 

 logy are used to designate these different relations, which I had 

 appHed to them two years before in treating of JjameUicprn 

 Insects.* 



The theoretical difference between affinity and analogy may 

 be thus explained if Suppose the existence of two parallel series 

 of animals, the corresponding points of which agree in some one 

 or two remarkable particulars of structure. Suppose also, that 

 the general conformation of the animals in each series passes so 

 gradually from one species to the other, as to render any inter- 

 ruption of this transition almost imperceptible. We shall thus 

 have two very different relations, which must have required an 

 infinite degree of design before they could have been made 

 exactly to harmonize with each other. When, therefore, two 

 such parallel series can be shown in nature to have each their 

 general change of form gradual, or, in other words, their rela- 

 tions of affinity uninterrupted by any thing known ; when more- 

 over the corresponding points in these two series agree iji some 

 one or two remarkable circumstances, there is every probabihty 

 of our arrangement being correct. It is quite inconceivable that 

 the utmost human ingenuity could make these two kinds of 

 relation to tally with each other, had they not been so designed 

 at the creation. A relation of analogy consists in a correspon- 

 dence between certain parts of the organization of two animals 

 which differ in their general structure. In short, the test of such 

 a relation is barely an evident similarity in some remarkable 

 points of formation, which at first sight give a character to the 

 sinimals and distinguish them from others connected with them 

 by affinity ; whereas, the test of a relation of affinity i^ its fornir 

 ing part of a transition continued from one structure to another 

 by nearly equal intervals. As a relation of analogy must always 

 depend on some marked property or peculiarity of structure, and 

 as that of affinity, which connects two groups, becomes weaker 

 and less visible as these groups are more general, it is not in the 

 least surprising, that what is only an analogicaji correspondence 

 in one or two important particulars, should often have been 

 mistaken for a general affinity. 



M. Fries draws the distinction between them precisely m the 



• I owe my acquaintance witli these several works, as well as much information on 

 points of which I should otherwise have been totally ignorant, to tlie friendship of the 

 consummate botanist, in whose possession the Banksian liibrary has been so worthily 

 deposited. The second part of the I/oice Entomologicce was published in April, 1821. 

 On the 24 th of the following month 1 first saw a copy of M. Decandolle's paper, 

 which was not published till some week* after ; and in the course of last wmter I first 

 saw Agardh's paper and the work of M. Fries on Fungi. If BI. Fries borrowed from 

 liis master Agardh the idea of distinguishing affinity and analogy, which is not impro- 

 bable, we must at least allow him the merit of having greatly improved this part of the 

 theory. 



•f* See Horce Entomologicce, p. 362 et seq. 



