Dr L. Mandl on the Scales of Fishes. lid 



cous cavities oi' 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 set- 

 tled ; we shall afterwards bring forward observations which 

 contradict the idea. " They are formed of corneous or cal- 

 careous plates or leaves, superimposed on each other, and 

 which are secreted at the svu^'ace of the chorion ; these leaves 

 successively attach themseh'es to the lower surface of the pre- 

 ceding ones, to which they become soldered by layers of in- 

 durated mucus." This is Leuwenhoek's idea, only he called 

 these leaves scales. " 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 con- 

 centric 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 concentric lines 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 of different sizes, but all retaining the shape 

 of the scale. These leaflets are disposed above each other in 

 such a manner, that the smallest occupy the centre of the 

 scale and form its exterior part, while the largest, with their 

 margin projecting beyond the preceding, are soldered succes- 

 sively to their lower surface. We thus see evidently that the 

 concentric lines visible on the surface of scales are simply the 

 edges of the leaflets composing them." The fact related by 

 M. Agassiz can refer only to the leaflets of the lower bed, 

 which are separated by maceration ; his conclusion, therefore, 

 is founded on a false interpretation, which, in other respects, 

 without the aid of the microscope, cannot be correct. All the 

 modifications observed in the form and nature of the surface 

 in scales, arise from the forms of the augmenting leaflets, and 

 the manner in which they are placed above each other. Layers 

 of enamel are deposited on the outside of some scales (as 

 among the Ganoides)." 



