24: 



EVENLN'GS AT THE MICROSCOPE. 



deposits from bencatli ; but that, after a few have been 

 deposited, thej begin to slit, probably by contraction 

 in becomins: solid ; that the lower layer is formed after 

 each upper one is hardened, exceeding its length by a 

 little, and filling np the slit ; that this lower layer be- 

 comes the upper layer of the next course, slitting, and 

 turning up its terminal edge as it hardens ; that then 

 the lower layer is deposited on this, filling up the slit 

 as before ; and that this process goes on as long as the 

 fish lives. 



It is curious that, in the scales of the Pike, the por- 

 tions thus separated by slitting, instead of expanding 

 and leaving spaces to be filled up, actually close over 

 each other, the divided j^arts overlapping considerably, 

 as you may see in these specimens. Tlie left hand scale 

 (a) is from the back ; tlic central one (5), which has only 



SCALES OP PIKE. 



a deep narrow incision instead of a tube, is from the 

 lateral line ; and the third (c) is from the belly of the 

 fish. 



Let us return now to the scales of our Gold-Fish, 

 and examine a hiirhlv interestino: structure connected 

 with them. The brilliant golden or silvery reflection 

 that constitutes the beauty of these lovely fishes, de- 

 pends not on the scales themselves, but on a soft layer 



