4 THE TERIODIC GROWTH OF SCALES IN GAUID^ 



Broussonet demonstrated the presence of scales in a number of genera of 

 fish in which their existence had either previously been denied or held in 

 doubt, for example Cepola, Remora, Ammodytes, Anguilla, Scomber. His 

 descriptions are very brief, and the paper is not of great importance.* 



We osve to Heusinger the first attempt at a classification of fish by means of 

 their scales. t He divided fishes provided with scales into five groups: — 



I. Fish with small scales entirely hidden in skin (Anguilla, Muraena, 

 Elennius, ^Muraenophis). 



II. Fish with scales properly so called (Carp, Esox, Salmo). 



III. Fish with scales strongly toothed at their free margins (Chsetodon). 



IV. Fish provided with osseous scales (Knochenschuppen). These scales 

 resemble those of Group II,; but they have so much calcareous matter as to 

 resemble hard teeth. They are not usually imbricated, but are isolated or 

 simply contiguous ; their surface is frequently furnished with spines 

 (Lepidosteus and several species of the genera Trigla, Cottus, Silurus, 

 Gasterosteus, etc.). 



V. Fish with osseous plates (Knoclienplatten). These plates form a solid 

 cuirass round the fish (Ostracion, Diodon, Syngnathus, Hippocampus, 

 Accipenser, etc.). 



Selachians are not comprised in the preceding five groups. Heusinger 

 places them in a separate division characterised by the "mode of conformation 

 of the spiny formation," whose structure approaches to that of teeth. 



Heusinger also gives a succinct description of true scales, and in regard to 

 their structure agrees with Agassiz in regarding each scale as composed of 

 superimposed lamelke or la^'ers. 



Kuntzmann's paper | is of importance chiefly because it contains the germ of 

 an idea which Agassiz later developed more fully in his Classijication des 

 Poissons. In his paper Kuntzmann opposes the views of Schaeffer, who had 

 enipliasised the differences between scales of the same fish. Kuntzmann held 

 " that though one does not easily find absolutely similar scales on the same 

 species of fish, yet the scale of each species has some characteristic feature, 

 and that an examination of scales may enable one to acquire a more exact 

 knowledge of species, and that one may identify some genera and even some 

 species simply by an examination of their scales." He compares scales to the 

 leaves on plants, in whicli, altliough there is frequently quite a degree of 

 variation among the leaves of the same species, still one may often recognise 

 the species of plant by means of its leaves. 



Kuntzmann experimented witli scales in regard to their indestructibility in 

 water, and showed that after prolonged immersion in water they were not 

 softened to any marked degree. 



He opposed the opinion of Leuwenhoeck as to the concentric lines on the 

 upper surface of the scale indicating the age of the fish. He maintained that 

 the scales of an old carp do not show a larger number of concentric lines than 

 tliose of the young carp (see lioffbauer). As to the mode of scale growth, 

 Kuntzmann agreed in the main with tlie views of Reaumur. He regarded the 

 small quadrangular plates (described by Reaumur) on the internal surface of 



* Broussonet, 1787. i Heusinger, 1823. + Kuntziuann, 1824. 



