Investigations into the structure and development of the scales and bones of fishes

Abstract

In this memoir the author first points out the discrepancies that exist between the opinions of M. Mandl and M. Agassiz respecting the structure and growth of cycloid and ctenoid scales; and after referring to the peculiar views entertained by each of these ichthyologists, he enters upon the investigation of a number of examples, including the Carp, Perch, Gray Mullet, Pike, Salmon, and especially the large scale of an unknown fish from the Bay of Dulse on the western coast of Mexico. The results of this inquiry lead the author to conclusions which differ considerably from those of both M. Agassiz and M. Mandl. He points out the existence of three distinct vertically-disposed structures in each of these scales; a lower one, consisting of membranous laminae; a middle calcareous one, having a very peculiar structure and growth; and an upper one, also calcareous, but very distinct from the last, and which is variously disposed in different scales. In all it contributes the peculiar cycloid and other markings which ornament their surfaces; whilst in ctenoid scales, isolated portions of it appear to form the characteristic teeth which project from their posterior margins. The author then developes in succession the peculiar and beautiful structures seen in the scales of Dactylopterus, Balistes, Loricaria, and various forms belonging to the Ostraciant group. Whilst these examples exhibit singular diversities of structure, they appear to be all modified forms of one common type.