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originated by Mr. Darwin, and now generally entei'tained by naturalists, in 

 regard to the " Origin of Species," for (as you will find in the sequel) I have 

 assumed that many of the principles of action which his theory is intended to 

 elucidate, are directly engaged in producing the changes which T propose to 

 notice, both as having been already effected, and as being likely to ensue in 

 the course of time. 



You are all doubtless aware, that organic nature is broadly divisible into 

 two great branches, namely, animal and vegetable life, the study of the former 

 being termed Zoology, and of the latter Botany. It is trae, that at the 

 extreme confines of each of these two kingdoms, as we descend from the higher 

 to the lower forms, even this broad distinction is apparently obliterated, and 

 we find, in effect, that naturalists were long in doubt to which of the two 

 kingdoms some of the lowest observed organisms, ought properly to be assigned. 

 This, however, is a matter which little concerns our present enquiry, though 

 it certainly helps to demonstrate the accuracy of that admirable analysis of the 

 organic world, which has lately been exhibited to us by our great physiological 

 writers, and from which we have learnt, not only that the infinite diversity 

 both of animal and vegetable life which peoples the globe, may all be brought 

 down to the primordial form of a single cell, but also that both may be reduced 

 into, and are, in fact, composed of the same elementary constituents. 



It had, however, been known long before reaching this more advanced 

 analysis, that the enormous multiplicity both of animal and vegetable life, 

 could, in each case, be reduced to a few types of construction, and, indeed, the 

 types thus established have constituted the bases of all those systems of 

 classification by the elaboration of which we have been enabled to study the 

 organic world in detail. 



Looking to the probability that the vegetable kingdom yielded to man his 

 earliest means both of sustenance and shelter, it has been assumed by every 

 writer on Natural History, that it was the first to engage his attention, and 

 become his study, and that the necessity of distinguishing between such forms 

 as were useful and such as were injurious, led to the first rude classifications of 

 vegetable life. " By placing together individuals apparently identical in form 

 (says Dr. Lindley), and having regard to the uses they could be applied to, 

 species were distinguished, and by applying a similar process to the species 

 themselves, groups analagous to what we now call genera were obtained. The 

 last step was to constitute classes, which were recognized under the well 

 known names of ' grass and herbs yielding seed, and fruit trees yielding 

 fruit.' " 



It will not be necessary for me to point out how, step by step, the more 

 complete systems of classification now adopted by naturalists were arrived at, 

 how the artificial system of Linnaeus was replaced by the natural systems of 

 succeeding enquirers, until we are gradually reaching a more exact knowledge 

 of the plan of nature, it being sufficient for my purpose to call your attention 

 broadly to those systems, and to the circumstance that, in every case, they 

 virtually terminate with what is called "species." 



The animal kingdom has been primarily divided into two great Sub- 

 kingdoms or Provinces, namely, the Yertebrata and the Invertebrata, each of 

 which has been again subdivided into classes, orders, families, and species. 



The vegetable kingdom has also been primarily divided into two sub- 

 kingdoms, namely, into asexual or flowerless, and sexual or flowering plants, 

 each comprising a number of distinct classes, orders, genera, and species. 

 With the latter term indeed, whether in the Animal or Vegetable Kingdoms, 

 classification proper has been supposed to end, although all systematists have 

 recognized the existence of varieties, even in a state of nature. 



Now it might be supposed, looking more particularly to our recent 



