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of his idea of species is invariably, "We reckon as many species as the Infinite Being created at the beginning." 16 And his authority was so powerful that the age of Voltaire and of Diderot devoutly accepted this obvious dogma, and transmitted it to posterity as a maxim impossible to question.

Linnæus was, however, so little of an anatomist that in this province Zoology required a completely fresh foundation, and, in the capacity of a second Linnæus, Cuvier stood forth." His school styles itself the school of facts, yet it was by no means without a tincture of philosophy. On the contrary, the definite and simple nature of his principles and deductions could not fail to be imposing. He epitomized the summary of his observations as "Laws of Organization;" and he applied the teleological view, the principe des causes finales, with great advantage to the knowledge and restoration of antediluvian animals. The question of the persistency or mutability of species thrust itself forcibly upon him. For this an external cause was given by the Egyptian expedition and the investigation of mummified animals. Etienne Geoffroy St. Hilaire and Lamarck attacked the persistency of species, and held that, especially considering the stability of external conditions, the Egyptian period was far too short for the identity of the mummies with the species now extant, to make it possible to infer the immutability of species; but the question was curtly despatched and silenced by the predominating school of Cuvier.

Meanwhile, Cuvier not only increased the accumulation of facts, but, as we have already hinted, he grouped them so happily and with such philosophical

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skill that he undoubtedly approached the object at which he aimed the Natural System. He supplied the first reliable information respecting extinct species. With regard to those which had replaced them in subsequent periods, he was not, as is generally supposed, an unqualified partizan of new creations, but he refrained from any fixed opinion. "I will not," he says, "positively affirm that for the production of the present animals a new creation was required. I merely say they did not live in the same locality, and must have come from elsewhere." Geoffroy Saint Hilaire, on the contrary, does not doubt that the animals now living are descended, by an unbroken succession of generations, from the extinct races of the antediluvian age.

Cuvier's method involved the danger of introducing dogmatism into natural science, and it is therefore justifiable to refer in this place to one of Cuvier's immediate disciples only recently deceased-Louis Agassiz, who in the most rigidly didactic manner adheres to the systematic categories, and invests them with fine-sounding definitions as "embodied creative ideas."19 According to him, species belong to a particular period in the world's history, and bear definite relations to the physical conditions predominant at the time, as well as to the contemporaneous plants and animals. Species are founded on well-defined relations of individuals to one another and the world in which they live, as well as on the proportions and mutual relations of their parts, and on their ornamentation.

Individuals, as representatives of species, bear the closest relations to one another; they exhibit definite relations also to the surrounding element, and their

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existence is limited within a definite period. Of gencra he says, "Genera are groups of animals most closely connected together, and diverging from one another neither in the form nor in the composition of their structure, but simply in the ultimate structural peculiarities of some of their parts." "Individuals, as representatives of genera, have a definite and specific ultimate structure, identical with that of the representatives of other species."

We may pronounce these definitions to be mere phrases, and inquire with Haeckel: "Of what nature are these 'ultimate structural peculiarities of some of their parts' which are supposed alone to define the genus as such, and to be exclusively characteristic of each genus? We ask every systematizer whether he may not equally well apply this definition to species, varieties, &c., and whether it is not finally the 'ultimate structural peculiarities of some of their parts' which produce the characteristic forms of the species, the variety, &c. In vain do we search in the "Essay on Classification" for a single example of the manner in which, for instance, the genera of oxen or antelopes, the races of hyænas and dogs, or the two great genera of our fresh-water bivalve shells, the Unio and Anodonta, are actually distinguished by "the ultimate structural peculiarities of some of their parts." Several of these definitions given by Agassiz may be interchanged point-blank, so general and merely negative are their statements. He characterizes the classes "by the manner in which the plan of the type is executed as far as ways and means are concerned." The orders, "by the degree of complication of the structure of the types." These phrases are interchangeable, but, like all dogma. tism, they make a great impression on those who from ignorance of the facts are incapable of criticising for themselves, and they are readily quoted to confute an unbelieving investigation of nature by one made in faith.

It might be thought that if the affair were so simple, and systematic ideas so firmly fixed, nothing would be easier than to establish the system. And so Agassiz maintains. He says that if a single species of any of the great animal groups were present, and admitted of investigation, the character of the type, class, family, genus, and species, might be determined. The weakness of this and similar statements may best be demonstrated by examining the basis of all dogmatic system, -the "species." If this idea be mutable, if the species be not given once for all, but variable, according to time and circumstances, the implications of the higher and more general ideas of genus, family, &c., must necessarily ensue. The keenest and most logical criticism on the deeply-rooted scholastic idea of "species" was made by Haeckel, after Darwin, in his classical work on the "Origin of Species," had completely exposed the old doctrine and practice of zoology and botany. In what follows we shall adhere to Haeckel.

We have seen above that Linnæus accepted the Creation as an irrevocable scriptural doctrine, and it is really absurd that many naturalists who have long abandoned any other dogma, should abide by this one. Therefore as the Bible mentions the creation of species, this legend was made the basis of all science. It is true there are not now many who appeal to scriptural testimony.

LINNÆAN DEFINITION OF SPECIES.

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Those who defend the stability of species rather imagine that, with Cuvier, they are entitled to interpret facts in their own favour; whereas they partly remain unconsciously involved in hereditary prejudice, and partly contrive to be deliberately blind to all that evidently contradicts the immutability of species.

Since Linnæus referred to the Creation, he attributed the individuals to a species, of which the pedigree ascended in direct line to the pair which proceeded from the hand of the Creator. Owing to the state of science in general, an examination of this pedigree was totally impossible in his time; and, indeed, with the strict reliance on sacred tradition, it was scarcely necessary. Cuvier, although a very unprejudiced and cool observer, nevertheless radically accepted the Linnæan definition of species. According to him, the species is the aggregate of individuals descending from one another and from common ancestors, and of those who resemble them as strongly as they resemble one another.21

"In this definition," says Haeckel, "to which the majority have ever since more or less closely adhered, two things are obviously required of an individual as belonging to a species: in the first place, a certain degree of resemblance or approximate similarity of character; and secondly, a kindred connection by the bond of a common descent. In the numerous attempts of later authors to complete the definition, the chief stress is laid sometimes on the genealogical consanguinity of all the individuals, sometimes on morphological uniformity in all essential characters. But it may be generally asserted that in the practical application of

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