CHAEACTEBS OF RECENT CEOCODILIA. 27 



distinguisliable into two layers. The more superficial of these is 

 thin, made up of irregular or formless connective tissue, and con- 

 tains many ramified pigment-masses. Its smooth outer siu-face un- 

 derlies the rete mucosum. Internally, it passes into the second or 

 deep layer, which consists of successive layers of distinctly fibrous 

 connective tissue, disposed in definite parallel bundles, and having 

 a very regular arrangement. Throughout a space corresponding 

 with the area of each scale, in fact, the bundles of each layer cross 

 those of the succeeding layer at right angles ; and the successive 

 tiers of bundles are tied together by short cords disposed perpendi- 

 cularly to the planes of the tiers. A corresponding arrangement of 

 the bundles of connective tissue has long been known to obtain 

 in the dermis of Fishes and Satrachia. At each end of this small 

 " mat " of connective tissue, the bvmdles, if I may so say, fray out ; 

 and at the anterior end, the layers, loosened in textiu-e, bend up- 

 wards, spreading out at the same time to become continuous with 

 the fibres of the " mat " in front. In consequence of the matting 

 under the quadrate surface of each scale, the dermis has a peculiar 

 facetted aspect, quite apart from any osseous deposit. Where 

 bony scutes are formed, they appear as very thin perforated plates 

 in the most superficial portion of the deep layer of the dermis ; so 

 that there is a single thin layer of dense connective tissue above 

 them, while below them are all the rest of the denser and deeper 

 lamellae of the dermis. Through the apertures in this primitive 

 osseous plate (the rudiment of the middle layer of the future 

 scute), bundles of connective tissue extend, connecting the deep 

 with the superjacent lamellae. 



If a thin section is made and decalcified with weak acid under 

 the microscope, the calcareous matter, as it is dissolved away, leaves 

 an obscurely fibrous matrix of a difierent aspect from the sur- 

 rounding connective tissue, and the endoplasts, or nuclei, of this 

 matrix are seen each to have occupied the centre of a lacuna. 



Again, the rudimentary scute lies in the dermis as in a sort of 

 pocket, the superficial and deep walls of which separate from it 

 with great ease ; and in good thin sections made through the der- 

 mis and scute, there seems to be no direct connexion between the 

 substance of the scute above and below, and the connective tissue 

 with whicli it is in contact. Nor could I satisfy myself that the 

 margins of the scute were continuous with the surrounding bundles 

 of connective tissue. However, the specimen had been a very 

 long time in spirit ; and I am unwilling to lay too much stress 

 upon these observations, which tend to negative the supposition 



