Fig. 36.—Rudolph Leuckart, 1823-1898.
From all these changes there resulted the seven primary divisions—branches, subkingdoms, or phyla—which, with small modifications, are still in use. These are Protozoa, Cœlenterata, Echinoderma, Vermes, Arthropoda, Mollusca, Vertebrata. These seven phyla are not entirely satisfactory, and there is being carried on a redistribution of forms, as in the case of the brachiopods, the sponges, the tunicates, etc. While all this makes toward progress, the changes are of more narrow compass than those alterations due to Von Siebold and Leuckart.
Summary.—In reviewing the rise of scientific natural history, we observe a steady development from the time of the Physiologus, first through a return to Aristotle, and through gradual additions to his observations, notably by Gesner, and then the striking improvements due to Ray and Linnæus. We may speak of the latter two as the founders of systematic botany and zoölogy. But the system left by Linnæus was artificial, and the greatest obvious need was to convert it into a natural system founded upon a knowledge of the structure and the development of living organisms. This was begun by Cuvier and Von Baer, and was continued especially by Von Siebold and Leuckart. To this has been added the study of habits, breeding, and adaptations of organisms, a study which has given to natural history much greater importance than if it stood merely for the systematic classification of animals and plants.
Tabular View of Classifications.—A table showing the primary groups of Linnæus, Cuvier, Von Siebold, and Leuckart will be helpful in picturing to the mind the modifications made in the classification of animals. Such a table is given on the following page.
L. Agassiz, in his famous essay on Classification, reviews in the most scholarly way the various systems of classification. One peculiar feature of Agassiz's philosophy was his adherence to the dogma of the fixity of species. The same year that his essay referred to was published (1859) appeared Darwin's Origin of Species. Agassiz, however, was never able to accept the idea, of the transformations of species.
| Linnæus | Cuvier | Von Siebold | Leuckart |
| Mammalia | Vertebrata | Vertebrata | Vertebrata |
| (Embracing five classes: Mammalia, Aves, Reptilia, Batrachia, Pisces.) | (Embracing five classes.) | (Five classes.) | |
| Aves | |||
| Amphibia | |||
| Pisces | |||
| Insecta | Mollusca | Mollusca | Mollusca |
| (Including Crustacea, etc.) | |||
| Articulata | {Arthropoda | Arthropoda | |
| {Vermes | |||
| Vermes | Vermes | ||
| (Including Mollusca and all lower forms.) | |||
| {Echinoderma | |||
| {Zoöphyta | {Cœlenterata | ||
| Radiata | { | ||
| {Protozoa | Protozoa |
Steps in Biological Progress from Linnæus to Darwin
The period from Linnæus to Darwin is one full of important advances for biology in general. We have considered in this chapter only those features that related to changes in the system of classification, but in the mean time the morphological and the physiological sides of biology were being advanced not only by an accumulation of facts, but by their better analysis. It is an interesting fact that, although during this period the details of the subject were greatly multiplied, progress was relatively straightforward and by a series of steps that can be clearly indicated.
It will be of advantage before the subject is taken up in its parts to give a brief forecast in which the steps of progress can be represented in outline without the confusion arising from the consideration of details. Geddes, in 1898, pointed out the steps in progress, and the account that follows is based upon his lucid analysis.