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Show ~36 EXPLANATIONS. reptilia occur in those early strata whe1·e th.ei·r remain1 :Ind vestiges are few. In as far as it may be taken as a positive fact, I only claim a modified benefit from it bP. cause the view which I take of the affinities and co~nec tions of the animal kingdom (and by ar.alogy of the vege .. table kingdom also) makes it a matter of less consequence than would be generally supposed, which order of any class appears first in the stone record, though still perhaps a matter of smne consequence. This vie.w suggests that developme~t has. not proceeded, as IS usually assumed, upon a single hne which would require all the orders of animals to be placed one after another, but in a plurality of lines in which the orders, and even 1ninuter subdivisions of each class, are ranged side by s·ide. It also suggests that the development of these various lines has proceeded independently in various regions of the earth, so as to lead to forms not everywhere so like as to fall within our ideas of specific character, but generally, or in some more vague degree, alike. The progress of the lines becomes clearest when we advance into the vertebrate sub-kingdom. '\Ve can there trace several of them with tolerable distinctness, as they singly pass through the four classes of Fishes, Reptiles, Birds, and Mammals ; the Birds, however, being a branch in some part derived equally with the reptiles from fishes, and thus leaving some of the mammal order in immediate connection 'vith the reptiles. The lines or stirpes have all of them peculiar characters which persist throughout the val'ious grades of being passP-d through, one presenting carnivorous, another gentle anJ Innocent animals, and so on. We have, therefore, in the animal kingdom, not one long range of affinities, but a number of short series, in each of which a certain general character is observable, though not always to the exclusion of the organic peculiarities of families in neighboring lines, especially in the class of reptiles. According to this view, the matrix of organic life is, ipeaking generally, the sea. Fluid, required for all em .. t>ryotic conrit tions, is also necessary to the origination ot the val·ious stirpes of both kingdoms. The whole of thE? lowest animal sub-kingdom (Radiata) is aquatic; so are nearly the Moll~ca and a very large proportion of the Articulata. In the Vertebrata, the lowest clasg also is DEVEL~MENT 0~.. 'ritE ANIMAL KINGDOM. 23? whoLy aquatic. The arrangement appears to be thisthe basis of each line is a series of marine form'J; the remainder consists of a series designed to breathe the atmosphere and live upon land, these being all of im· ptoved organi-tation. The classification which this system implies rrtay be said to be transverse to all ordinary classifications. The invertebrate, ichthyic, reptilian, ornithoid, and mammalian characters are horizontal grades, through which the lines pas3, and where they send off brancheJ; not separate and independent divisions. In any of these branches where we have a clear knowledge of the various forms, it is po3sible to trace the affinities, in conjunction with an improved organization, through genera which are adapted to a partially marine life, to a residence in the mouths of rivers, or on shores and muddy shallows, then th;:ough ~enera which are, in succession, appropriate to mat·shes, Jungles, dry elevated plains, and mountains. And it is this series of external conditions and adaptations which has caused that system of analogies between various families of animals which has of late attracted attention. But•the im1nediate cause of the development of each line through its various general grades of being is to be sought in an internal impulse, the nature of which is unknown to us, but which resembles the equally mysterious impulse by which an individual embryo is passed- through tts succession of grades until ushered into mature existence. Geology shows us each line taking a long series of a9es to ad vance from its humble invertebrate effluents to 1ts highest maxnmalian forms; and this I have ventured to call " the universal gestation of Nature." The traces of this order of the animal kingdom have been seen in all ages of science. Every zoologist acknowledges the grauations and affinities which appear amongst animals. Prompted by what so palpably rneets observation, many have tried to range the various orders or families in one line, or (to use the favorite phrase) chain of being; ·but they have always failed, which is not to be wondered at. One cause why zoologists have not up to this time thought of trying any different arrangement, is the confusion arising from prevalence amongst many families of parallelisms of structure, which have been regarded as affinities, when in reality they are only identical characters demanded by common |
