252 The Edinburgh New Philosojj/ucal Journal. 



Dr. Mandl observes, that the merit of having first called 

 the attention of naturalists to scales, is due to M. Agassiz ; 

 but being deprived of the aid of the microscope, not only 

 the organization of the scale remained concealed from him, 

 but he inevitably confounded scales of the most different 

 forms. Nothing, says Dr. Mandl, can be more different 

 than the scales of the Muges, Atherines, and Cyprini, though 

 all comprised in the same order by M. Agassiz, on account 

 of a supposed conformity of structure of their scales. Yet 

 Dr. Mandl thinks the study of scales may be made the 

 foundation of a natural arrangement of fishes ; just as much 

 we should say, as the study of any other part admitting of 

 an equal facility for examination. It is singular how com- 

 pletely averse the naturalists of the Continent are to the 

 adoption of the more general method of viewing subjects 

 of this nature. An organ, whether it be a tooth, fin, wing, 

 or scale, an eye, or a mouth, can only become the founda- 

 tion of a natural system of classification when it is found to 

 present peculiarities sufficient to mark the structure of the 

 species to which it belongs. Scales appear to Dr. Mandl 

 to be sufficient for the natural classification of fishes, but 

 the microscope is required to reveal their form, and in conse- 

 quence of not having used it, the results of M. Agassiz are 

 in some degree vitiated. 



In all ordinary cases, the value of characters depends 

 on their being easily accessible and plain. If, for instance, 

 we have as many points to take into account in determining 

 between two scales, as between two entire specimens of the 

 animals they belonged to, the difficulties of the case would 

 remain pretty much the same, while there might be additional 

 chances of error on the side of restricting our means of com- 

 parison within too narrow limits. It is in researches re- 

 garding fossil fishes, that the form of scales has proved so 

 important, and it may be doubted whether the results would 

 be rendered more striking under a more rigorous use of the 

 microscope. 



