Causes of Formation of Different Forms of Vertebræ

Abstract

IN Vertebrata we generally find three forms of vertebræ, namely, proçlous, ophisthoçlous and amphiçlous. In the case of fishes, we get exclusively the amphiçlous form. In birds and mammals the vertebræ approach more nearly to the amphiçlous form than to other types. In the case of Amphibia and Reptilia we get all the three forms in different species, and in the latter class sometimes we get all the three forms even in one individual. The importance of the question is self-evident, as different forms of vertebræ furnish characters diagnostic and useful for classification.