Jeffries.] 236 [February 7, 



bryo, and in reptiles occur promiscuously over the body as the re- 

 sult of physico-physiological causes. The minute structure of the 

 two is never the same. The embryological resemblance has al- 

 ready been shown in the descriptive portion to be the result of 

 necessity; any appendage must be covered by them and they 

 themselves have here no value. 



But various other facts point against any such morphological 

 relations. Scales undergo a regular moult and renewal, scuta 

 do not. Scuta bear epidermal appendages, feathers, — scale 

 never do ; thus pointing to scuta as simple folds of the skin, not 

 as appendages. The toe-pads which have no resemblance to 

 scales may be seen on the sides of the toes of any bird with small 

 scuta to pass over into scuta. Hence, were the theory true, 

 the toe-pads must be scales, which is an absurdity. Again the 

 scuta of birds resemble the cutaneous flaps on the opossum's 

 tail to a wonderful degree. Their form and arrangement is pre- 

 cisely the same, both bear true appendages, and both have the 

 same histological structure. Like the scuta the opossum flap has 

 a mucous layer and outer horn coat with a mesodermal core. 

 Hence, if resemblance is of any value the flaps on the opossum's 

 tail must be scales if scuta are scales. Yet no one would dare 

 to call the former scales. 



Spurs on the wing and tarsi are special modifications and occur 

 in such diverse groups of birds and yet in limited numbers that 

 they must be regarded as of recent origin in the separate groups 

 where they exist. 



They are not to be classed as modified scuta as has been done 

 by those who consider scuta and scales to be the same thing. 

 The wing spurs and tarsal spurs are like organs ; thus the theory 

 would require the existence on the wings of birds of scales ready 

 to be evolved into spurs in a few isolated cases. Spurs, therefore, 

 are in the whole group analogous organs, but the spurs of the 

 pheasants, for instance, are inter se morphologous. 



Though perhaps not in place here, I would suggest that the 

 first function of these spurs is as claspers not as organs of offence. 

 By this means their existence in the developing stage is ex- 

 plained. 



Combs, wattles and the like must also be regarded as recent 

 structures of no general morphological value. 



