Page:Popular Science Monthly Volume 22.djvu/207

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or common origin. Nor is it an unfortunate circumstance that coal-tar can not be used as a substitute for bitumen, since the former contains many constituents that are more valuable for other purposes, while Trinidad offers an inexhaustible supply of the latter.

 
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SPECULATIVE ZOÖLOGY.
By Professor W. K. BROOKS,
OF JOHNS HOPKINS UNIVERSITY.
I.

AT a time when most naturalists who venture at all beyond the facts of life-science are busied with the attempt to trace the relationship between the various groups of living things, and to express this relationship in a tree-like system of classification, it is startling to hear from one of the highest authorities on life-science the statement that "the time for genealogical trees is past. . . . It seems hardly credible that a school which boasts for its very creed a belief in nothing which is not warranted by common sense should descend to such trifling."[1]

It is true that the context seems to show that the author does not visit all attempts at phylogenetic classification with the sweeping condemnation which the passage quoted seems to imply, yet the fact that a high authority upon the subject has made such a statement at all is a sufficient reason why those who believe that the status of modern morphology is not without a basis of common sense should carefully revise their grounds for this belief, in order to decide for themselves how far, and in what shape, such speculations upon the relationships of organisms are admissible, and favorable to the progress of science.

The belief that the present life of the globe is only a very small part of its total fauna and flora is hardly more firmly fixed in the minds of the present generation of naturalists than the belief that the recent species are the modified descendants of those which are extinct; and there are few who would not acknowledge that their conception of the origin of life would be fairly illustrated by comparing the living things of the past and present to a great, many-branched tree, buried in the ground so that only a few scattered groups of twigs are exposed to our direct observation, although these groups show by their arrangement a vague and indefinite relation to the branches below the ground. The twigs which are exposed are the living things which now people the earth, and those twigs and branches and larger trunks which

  1. "Embryology and Paleontology," by Alexander Agassiz. Address before the American Association for the Advancement of Science.