Dental cosmos . s, and has nothingto do with the theory of coalescence. Indeed, this new theory is notconvenient to the paleontologists. A large series of phenomena,which at present are regarded as well-established facts, have to bere-examined with respect to the theory of coalescence. Paleontolo-gists, in their investigations, rely chiefly upon a careful study of theexternal shape of the fully-formed tooth. This is one way of ascer-taining the truth, and the results obtained by such workers as Copeand Osborn show us what can be attained by it. If the fossils of themammalian ancestors were pre
Dental cosmos . s, and has nothingto do with the theory of coalescence. Indeed, this new theory is notconvenient to the paleontologists. A large series of phenomena,which at present are regarded as well-established facts, have to bere-examined with respect to the theory of coalescence. Paleontolo-gists, in their investigations, rely chiefly upon a careful study of theexternal shape of the fully-formed tooth. This is one way of ascer-taining the truth, and the results obtained by such workers as Copeand Osborn show us what can be attained by it. If the fossils of themammalian ancestors were present in an uninterrupted series, wecould form from that our final conclusions. But we know how incom-plete the paleontological records are. Imagination has free play atpresent, and fills up the gaps with more or less success. It is easy,then, to confound analogies with homologies, to confuse the secondarytubercles of teeth with the primary tubercles, especially when aworker starts with a prejudiced mind. Fig. Fig. 8.—Spelerpes {Geotriton)fuscus. Sagittal section through the dental plate lying uponthe parasphenoid. Z, fully-formed tooth ; C, cement of the common dental plate ; , para-sphenoid ; E, epithelium of the buccal cavity ; ZL, end of the dental ridge ; K, cartilage. 90 diam. In such cases evolution is the safest test. Copes trituberculatetheory was a well-established scientific fact only from the momentwhen it was confirmed by evolution. Evolution gives us the proofthat the molars of reptiles and mammals have arisen by the fusion ofseveral unituberculate teeth. This is seen most plainly in the caseof the simply constructed reptilian molars. The opposite view, thateach molar develops by the transformation of a single unituberculatetooth, is purely arbitrary. A paleontologist or comparative anato-mist, who judges only from the external shape of the fully-formed teeth,would probably have quoted this very dentition of the Chamaeleonas proof for the theory of tran
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