PART VIII 



PROBABLE CAUSE OF THE LOSS OF THE 

 CALCAREOUS ARMOUR IN MAMMALS 



Before entering into this discussion, it may serve some purpose 

 to go over some of the points discussed in the foregoing pages. 



A glance at the three Figures 4 to 7 shows that the groups of 

 spots on the abdominal surfaces are much more altered than those 

 on the back and flank. This, in my opinion, as I have often 

 stated, has resulted from the abdominal armour having been got rid 

 of before the dorsal armour, so that the abdominal rosettes had time 

 to alter before the dorsal pigment-rosettes had come into exist- 

 ence, because the dorsal region was still covered by a carapace. 

 In other words, the ventral spots of the Leopards are much more 

 ancient, and consequently more modified than the dorsal rosettes. 



One might suppose the process of dispensing with armour- 

 plating was something after this fashion : — The remotest vertebrate 

 ancestor was plated top and bottom, like the Ganoid fishes and 

 the Crocodiles. 



Mr. Alfred Russel Wallace^ says that, in skinning the Jacari 

 — an Alligator six feet long — ' the scales of the belly could only 

 be cut by heavy blows with a hammer on a large knife,' and that 

 he ' was obliged to borrow a drill to make the holes to sew up the 

 skin,' after stuffing it. 



Then the complete rachitis of the skin occurred first on the 



■^ Travels on the Amazon (Rio Negro), p. 219. 



