34 EVENINGS AT THE MICROSCOPE 



trie marks in the former are much coarser and less regular, 

 often being interrupted, and seeming to run into each other, 

 and frequently swelling into oval scars. This may, per- 

 haps, be owing to the surface having been partially worn 

 down by rubbing against the gravel of the bottom, or against 

 other objects in the water. Besides the concentric lines, 

 there are seen on many o~f the scales, especially those of the 

 lateral line, radiating lines varying in number from one to 

 twenty, or more, diverging from the centre toward the cir- 

 cumference, and frequently connected by cross lines form- 

 ing a sort of net-work around the centre (see c). Under 

 the microscope, these lines appear to be elevated ridges, 

 dividing the concentric lines; but of their use I am ignorant. 

 What I have just stated is the ordinary explanation 

 of these fine concentric lines; but a careful examination of 

 the structure with much higher powers than we have been 

 using induces me to doubt its correctness. Eeverting to the 

 scales of the Perch, let us notice the clear diverging bands, 



which look as if the whole 

 scale had been split in sev- 

 eral places, and the openings 

 thus made filled with uniform 

 clear substance. The same 

 structure is seen in many other 

 scales, as in this cycloid one 

 from the Flounder, which, be- 

 OF FLOUNDER. ing coarsely lined, shows the 



a, Natural size. . n 



structure well; or in these 



from the Green Wrasse. I will now apply to one of these 

 a power of 600 diameters, concentrating the light thrown 

 through the scale from the mirror by the achromatic con- 

 denser, and examine the scale anew. You now see two 



