The Edinburgh New Philosophical Journal. 253 



" M. Agassiz, in recent times, has strongly drawn the attention of 

 philosophers to the form of scales, by assuming them as the basis 

 of his classification. After having said a few words, in the work 

 quoted below, on the structure of the skin, he speaks first of the 

 position of scales, and then of their form. 



" M. Agassiz explains the different forms of imbrication, without en- 

 tering into details on the disposition of the skin, and continues thus : 

 ' It results from this that the position of the scales varies much ; how- 

 ever, we can usually distinguish pretty regular series, which enable 

 us to determine their position with accuracy, particularly in the case 

 of imbricate scales. The series are disposed obliquely from the fore 

 part backwards, from the middle of the back to the middle of the 

 belly ; these series may be called dorso-ventral. It is necessary further 

 to distinguish the superior and inferior demi-series, and I would call 

 those which extend from the lateral line to the back medio-dorsal, and 

 distinguish the anterior and posterior medio-dorsal, according as we 

 wish to indicate those which are directed from backwards, or those 

 which are inclined from behind forwards. The same thing shoidd 

 be done with the series below the lateral line, which I call medio- 

 ventral, such as extend from the lateral line backwards or downwards, 

 being the posterior medio-ventral, and those directed forwards anterior 

 medio-ventral. 



" ' Scales,' continues M. Agassiz, ' are contained in the mucous 

 cavities, or in small bags formed by the chorion, to which, however, 

 they do not adhere by means of vessels.' We may observe that this 

 point by no means appears to us to be settled; we shall afterwards 

 bring forward observations which contradict the idea. ' They are 

 formed of corneous or calcareous plates or leaves, superimposed on each 

 other, and which are secreted at the surface of the chorion ; these 

 leaves successively attach themselves to the lower surface of the pre- 

 ceding ones, to which they become soldered by layers of indurated 

 mucus.' This is Leuwenhoek's idea, only he called these leaves scales. 

 1 In order to form an accurate notion of this development, it must 

 be first examined in genera of fishes, in which the scales appear to 

 present these dispositions in the most simple state ; for example, the 

 eel, blennies, cobitis, and leuciscus. . . . It is easy to convince 

 oneself that the concentric lines of the anterior edge and those of the 

 posterior edge are continuations of each other.' Nothing can be more 

 opposed to M. Agassiz's opinion than the scales mentioned, the con- 

 centric hues of which are nothing more than insulated cells. 



" ' After macerating scales for some time in water, they can be easily 

 divided into a great number of plates or leaflets, more or less thick, and 



