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 250 THE SCIENTIFIC MONTHLY

our attention chiefly on tasks and problems that are of immediate prac- tical importance. On the contrary^ as we survey the history of science, we see clearly that inquiries into the causes or beginnings of things, irrespective of direct utility, are of the first importance. It is these which lead to the emergence of the great general ideas, which, in their turn, light the way to the discovery of special facts that are of direct utility.

Turning from the utilitarian aspect of biology, let us take up for a moment a problem which, never new, is yet always interesting. What is the origin of all these forms that we have learned to know? What is the nature and origin of species, or, choosing the phraseology of the day, of specific differences?

In the histories of the theory of evolution we read, wondering if any of our present-day notions shall prove as untenable, that Idnmsus held that species were changeless, that they were in character and number precisely as originally created. We read that somewhat later, when fossils were better known, Cuvier interpreted the present organisms and the very different ones of past geological periods as the results of separate acts of creation, each period with its living things coming to an end in some tremendous catastrophe. And that still later Louis Agassiz held the same view, while meantime he with many others paved the way for evolution by discoveries of fact, bringing to light the exist- ence of fossil series from low forms to high, and many illustrations of the generalization embodied in our biogenetic law of to-day, namely, the generalization that organisms do not pursue a straight path of devd- opment from egg to final form, but commonly develop temporary pecu- liarities of structure constituting resemblances to lower forms.

The strong tide of evolutionary doctrine that set in with the publi- cation of Darwin's great book in 1859 brought nothing new to what had been taught by Louis Agassiz as regards the existence of the resem- blances, just alluded to, between organisms, adult, embryonic and fossil. But that the stream of living matter has been continuous from gener- alized type to derived form, or, as we say, from ancestral type to de- scendant, this is the conception that rings out the note of difference from Agassiz's teaching. Basing its argument on minor mutabiliiy that can be demonstrated and on a mass of circumstantial evidence, overpowering in its cumulative effect, evolution claimed that funda- mental resemblance is not a transcendental likeness, but is due to kin- ship. With this conclusion we are long familiar. It has entered into the very marrow of our mental life, and everything that we learn cor- roborates it. The conclusion concerns us in a direct way, for the evolu- tionary process can not be thought of as something finished and done with. Bather do we conclude that if organisms have changed, they are still changing.

Granted the fact that organisms change, the question veers and we

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