the Nalural Distrilution of Jnsecls and FungL igg 



regnimi, ordinem, genus, &c. in systemate ut individuum 

 esse sumendmn;" — in other words, that class bears the same 

 relation to class which order does to order, and genus to genus ; 

 tlien the number of groups composing a?iy group of the next 

 higher degree must be determinate ; and it only remains for the 

 naturalist to discover from observation what this number is. 



That Nature has made use of determinate numbers in the 

 construction of vegetables has long been known empirically ; 

 as for instance, where botanists have found the typical number 

 of parts of fructification in the acotyledonous plants of Jussieu 

 to be two, that in monocotyledonous plants to be three, and 

 that in dicotyledonous plants to be five, or multiples of these 

 numbers. Consequently the existence of a determinate num- 

 ber in the distribution of the plants themselves might have 

 been argued a priori. And in this manner indeed M. Fries 

 appears to have argued ; for it is tolerably clear that it was 

 the consideration of the foregoing rule, adopted by Nature in 

 the structure of acotyledonous plants, which induced him 

 theoretically to assume four as a multiple of two to be the de- 

 terminate number in wliich Fungi are grouped*. I say tliis, 

 because he is obliged from actual observation to admit that of 

 these four groups, one is excessively capacious in comparison 

 with the other three, and is always to be divided into txw. So 

 that we may either, with M. Fries, consider every group of 

 Fungi as divisible into four, of which the largest is to be rec- 

 koned as two, — a supposition that would not only make two 

 determinate numbers, but which, from the binary groups not 

 being always analogous, will moreover break the parallelism of 

 corresponding groups, — or we may account every group as 

 divisible into five, and thus not only agree with M. Fiies's ob- 

 servations, but besides keep the parallelism of analogies unin- 

 terrupted. If in this state of the matter it coukl now be 

 shown, that in the animal kingdom the same law is followed 

 by nature i in short, to take an instance, if it could be proved 

 that the Aniiulosa may either be divided into four groups, viz. 

 Ametabola, Cruslacea, Arachnida and Ptilota, where this last 

 is remarkably cajiacious and divisible into two natural groups, 

 viz. Mandibuluta and Haustdlata, or that aniuilose animals 

 may be divided at once into five groups of the same de'>ree, 

 but of which two have a greater affinity to each other than 



* It oiifilit licre to be observed, that Ockcn had [)revioiisly advanced tlie 

 opinion that four was tlie deteriiiiiiate nmiibcr in natural distribution. This 

 naturalist, however, having in his X//luigcxc7iif/ilefui- sc/tii/cii, lately pub- 

 lished, in a great nieasin-e abandoned the number four for five, and that more 

 especially in the animal kingdom, has thus got into all the difiiculties which 

 necessarily attend the sn[)position of two determinate numbirs. 



they 



