AS AN INDEX OF AGE. 5 



the scale as a precipitate, a deposit of mucus, which contributed directly to 

 the formation of scales. He differed, however, from Reaumur as to the 

 situation of these quadrangular plates later, affirming that they were contained 

 between two membranes on the internal surface of the scale, and not in vessels. 

 He held that growth does not take place at the edge, but over the entire scale, 

 and that this mode of growth is a consequence of the structure which the scale 

 shows at the time of its first formation, for the scales of a young fish and those 

 of an old fish are not essentially different except in size. He thinks that this 

 mode of formation allows one to explain the difference between scales of 

 different species, especially the difference of the concentric lines, which may be 

 wide or narrow, straight or curved, entire or interrupted in the different species. 

 Kuntzmann worked out a classification of scales into seven classes, remark- 

 ing at the same time that quite gradual transitions existed between these 

 classes, and that certain scales might equally well be placed in one class as in 

 another. His classes are the following : — 



I. Memhranoxis scales {IiauHgen Scliuppen). Scales which do not show 

 concentric lines (Gadus Iota). 



II. Semi-memhranous scales (halhhautu/en). Scales with a membranous 

 posterior portion, but with the anterior portion marked out by incomplete 

 concentric lines, crossed over by other lines running longitudinally {Clupea 

 harengus). 



III. Simj^le scales {einfachen). Scales with concentric lines covering their 

 entire surface without those lines forming any definite design by other lines 

 crossing over them (Sahno salar). 



IV. Scales icith a design {gezeichneten). Scales in which the concentric lines 

 on the scale surface form a regular design due to the arrangement of the same 

 (Murwna anguUla). 



V. Scales divided into several regions (gefelderten). Scales on which there 

 exist numerous ornaments which parcel out the scale into four well-defined 

 fields. These diverse fields, usually triangular in shape, meet at a point, which 

 is usually at the same time the centre of the concentric lines {Cyprinus 

 carpio). 



YI. Scales icith prickles. These scales are also frequently divided into four 

 fields. The posterior field bears spines on a more or less extended portion of 

 its surface, or sometimes only at its free border. These spines fall oft' on pro- 

 longed maceration, showing that they are not really portions of the scale, but 

 arise from the skin which covers the scales. These spines also fall oft" natur- 

 ally at certain seasons, and others take their place. "This fact seems to 

 establish a kind of moulting, such as occurs in Amphibia." Examples — The 

 scales of Scorpcena. 



VII. Spinous scales (gedornte) are also divided up into several areas or fields. 

 The spines are in this case, however, true prolongations of the scale, and do 

 not become detached on maceration. Example : — Perca lucioperca. 



Kuntzmann gives a short description of each type of scale with a corre- 

 sponding figure. Although the preceding classification is interesting, yet it 

 leads to an artificial comparison. 



Ehrenberg described the crystals of silvery matter previously described liy 



