Page:Popular Science Monthly Volume 77.djvu/148

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ANATOMY AND PHYSIOLOGY IN INVERTEBRATE EXTINCT ORGANISMS

HE inquiry into the position of anatomy and physiology in invertebrate paleontology seems very appropriate at present, since paleontology is steadily becoming more closely affiliated to zoology, and the sphere of zoology is at present dominated by comparative anatomy and physiology.

Since, however, invertebrate paleontology has only the hard parts, mostly outer shells, at its disposal, the view still prevailing among zoologists that little is to be expected from it in regard to the solution of the problems of anatomy and physiology of the lower animals seems natural. Nevertheless, the results already attained prove that if paleontologists do not approach their material with a geological knowledge only, as has been done in the past altogether too often, most gratifying results may be obtained, at least in some classes, for it must be conceded that the connection of the hard parts with the fleshy parts is very unlike in different classes; it is very intimate in some, as the crinoids and brachiopods, and again more indifferent, as in the gastropods.

But it is not claiming too much for invertebrate paleontology if we say that where the hard parts are of great structural importance, paleontology has earlier taken cognizance of this fact and consequently gone ahead of zoology. As an instance I may cite Zittel's investigations of the skeleton of the hexactinellid sponges which have taught the fundamental importance of the form of the spicules and the structure of the skeleton in that class and whose results have been readily adopted by zoologists. In classes which, as the brachiopods and crinoids, are to-day mere shadows of their former greatness, paleontology has its greatest chance, and it would fail in its task if it would there not become the instructor of the affiliated science; and it is gratifying to see that this fact is finding recognition, as, for instance, in Ray Lankester's "Treatise of Zoology," where the chapter on the crinoids has been entrusted to Bather, a paleontologist and one of the best authorities on crinoids.

It is apparent that in such classes as those just mentioned, of which only the last ends of the branches are still alive, the origin and nature