284 RAMBLES OF A GEOLOGIST. 



to pass through the scale. Whatever their use, they existed 

 merely as communications between the cells of the middle 

 cancellated layer and the surface. In a fish of the Chalk, 

 Macropoma Mantelli, the exposed fields of the scales are 

 covered over with apparently hollow, elongated cylinders, as 

 the little tubes in a shower-bath cover their round field of 

 tin, save that they lie in a greatly flatter angle than the tubes ; 

 but I know not that, like the pores of the Dipterians and the 

 Megalichthys, they communicated between the interior of the 

 scale and its external surface. Their structure is at any rate 

 palpably different, and they bear no such resemblance to the 

 pores of the human skin as that which the Palseozoic pores 

 present. 



The amount of design exhibited in the scales of some of 

 the more ancient ganoids, design obvious enough to be clear- 

 ly read, is very extraordinary. A single scale of Holopty- 

 chius Nobilissimus, fast locked up in its red sandstone rock, 

 laid by, as it were, for ever, will be seen, if we but set 

 ourselves to unravel its texture, to form such an instance of 

 nice adaptation of means to an end as might of itself be suf- 

 ficient to confound the atheist. Let me attempt placing one 

 of these scales before the reader, in its character as a flat 

 counter of bone, of a nearly circular form, an inch and a half 

 in diameter, and an eighth-part of an inch in thickness ; and 

 then ask him to bethink himself of the various means by 

 which he would impart to it the greatest possible degree of 

 strength. The human skull consists of two tables of solid 

 bone, an inner and an outer, with a spongy cellular substance 

 interposed between them, termed the diploe, ; and such is the 

 effect of this arrangement, that the blow which would frac- 

 ture a continuous wall of bone has its force broken by the 

 spongy intermediate layer, and merely injures the outer table, 

 leaving not unfrequently the inner one, which more especially 

 protects the brain, wholly unharmed. Now, such also was 



