44 THE PEKIODIC GROWTH OF SCALES IN GADID.E 



take place, for he says, "An clem vorliegenden Oltjecte, welcher fiir die 

 Untersucliung der scloroblastischen Processes in Fliiclienbilde sich vortrelllich 

 eignet, konnte ich nichts wahrnehmen, was zu Gunsten der Annahnie spriiclie, 

 dass Zellen in toto in das Product aufgingen ; die Kerne zeigten keine 

 Veranderung, ich sehe daher in der Bildung der Hartsubstanz einen Abscheid- 

 ungsprocess." In regard to the above, Ussow reiterates, "Alles das ist mir 

 ganz unklar." 



According to Ussow, the further development of the first layer of the scale 

 takes place in the following manner : — 



The cells overlying the substance of the first layer of the scale already 

 secreted appear to waste themselves down more rapidly than the lower cells 

 from the product secreted by them, so in the following stages one frequently 

 sees a transparent strip of homogeneous substance in the position of the 

 future scale ; underneath this transparent strip and immediately united with 

 it lies a row of scleroblasts with easily observable nuclei ; on the upper side of 

 the clear strips, on the contrary, one only sees three or four cells, the size of 

 whose nuclei as compared with those of the lower scleroblasts is distinctly 

 smaller. In still later stages one only meets with one or two such nuclei, and 

 those much smaller than the nuclei of the lower scleroblasts. In section- 

 cutting also it is easily seen that the overlying nuclei readily become loosened 

 from the clear strips of the first layer of the scale, while, on the contrary, 

 those elements lying beneath the clear strips form part of the latter, and 

 never loosen themselves from it. In following stages the size of the under- 

 lying scleroblasts decreases, and at length there only remain, as in the case 

 of the overlying cells, long extended, closely adjacent nuclei without trace of 

 plasma, on which the first layer of the scale is formed. 



Summary of preceding development. 



(1) The cells of the papilla arrange themselves in two layers, the upper 

 and under; between these two layers there appears a thin strip of refractive 

 substance, the substance of the first layer of the future scale. 



(2) The cells of the upper layer (the over-lying scleroblasts) use them- 

 selves up in the formation of scale material (its first layer) more rapidly than 

 those of the under layer (the underlying scleroblasts) ; in consequence of this, 

 one gets the stage of a plate with cells of the lower layer apparently enclosed 

 therein. 



(3) The first layer of the scale is apparently the product of the scleroblasts, 

 that is to say, it is due to the change of the plasma of the latter into dentine- 

 like substance. 



About this time, when the first layer of the scale is quite complete, the 

 change of its position in the dermis commences. Its posterior end (that 

 turned towards the tail of the animal) raises itself gradually and presses 

 on the epidermis ; the anterior end, on the contrary, becomes sunk in the 

 deeper layers of the dermis. This change in the position of the scale comes 

 about through the formation of the so-called ^^ scale pockets." Between the 

 plates of scale substance there exist free portions of the dermis which lie 

 close on the epidermis in these intervening spaces, and contain small 



