54 THE TERIODIC GROWTH OF SCALES IN GADID.E 



I must conclude my review of the literature of scales, so far as it bears on 

 the subject of my investigations, with a notice of a preliminary paper by Dr. 

 Marett Tims.* This paper deals with later stages of scales than those of 

 Klaatsch and Ussow. 



The scales observed by Marett Tims were from several species of Gadidse — 

 Gcuhis inrens, G. luscus, G. j^ollachius, G. callarias, etc. As this paper is very 

 brief, I content myself mainly by quoting several of his sentences. 



"The formed scale is a compound structure consisting of a fibrous stratum, 

 upon the upper surface of which are situated numerous ' scalelets,' arranged in 

 lines radiating from a more or less homogeneous centrum. It is the presence 

 of these structures that gives the ' sculptured ' or ' ringed ' appearance to the 

 scales ; but these terms, though frequently applied, are misleading." 



"The fibres (of the fibrous stratum) are arranged in definite layers: (1) a 

 superficial, in which the bundles are concentric ; (2) a deep layer, in which the 

 individual bundles interlace with one another at right angles, each set running 

 diagonally to the long axis of the scale. A third layer, the fibres of which 

 form an irregular network, is possibly present, but it is much more difficult to 

 demonstrate." 



"The scalelets, placed upon the upper surface of the fibrous stratum, are 

 themselves covered with a delicate epidermis. . . . They consist of flattened, 

 imbricated, calcareous plates." 



He infers from reactions with borax-carmine and acid that in the earlier 

 condition the scalelets " are more thoroughly calcified, or rather, perhaps, that 

 in the later stages they contain a larger amount of organic material, and thus 

 stain more readily." 



" Between the radiating lines of scalelets the deeply stained fibrous stratum 

 is seen, resembling the spokes of a wheel. 



" In an early stage, before the scalelets become imbricated, the fibres may 

 also be noticed as transverse bands passing between the individual plates of a 

 row. 



" On examining a section of an undecalcified scale, the scalelets are seen to 

 be for the most part implanted in .sockets on the upper surface of the fibrous 

 stratum with a varying inclination. Those at the centrum appear to have 

 fused, forming a horizontal plate, while at the periphery of the scale they are 

 almost perpendicular. In a section through the skin of a green cod about 

 4 cm. long the individual scalelets are quite isolated. Each consists of a basal 

 plate, from the upper surface of which projects a minute spine, thus resembling 

 a small placoid scale. 



" Such a condition is only evident in material from which acid has been 

 rigidly excluded. The condition does not appear to have been previously 

 noted ; the figures given by Klaatsch and others being similar to those which 

 I obtained from material which has been pas.sed through acid alcohol, and 

 wliich do not show the true nature of tlie scale." 



If the forecasts of the results of this paper are true, they necessarily invali- 

 date many ideas previously held as to the nature of scales, and must also 

 introduce quite a new set of terms in their description. I prefer, however, to 

 keep cautiously to the older and more established views and terms until 



* Marett Tims, 1902. 



