ORIGIN OF WHALEBONE 115 



being this : that in all cases of highly specialised organs they are 

 nothing more than an abnormal development of rudimentary 

 structures always to be found in the generalised forms. Thus 

 you trace the baleen, which is a most peculiar specialisation, to a 

 development of certain " papillae " which are to be found in the 

 palate-structure of all the mammalia. 



I need not say that this (so far as it goes) agrees with my idea 

 that, on the evolution hypothesis, we ought to find structures on 

 the way to functional importance, as well as structures on the way 

 to final disappearance and extinction. Of course mere papillae 

 are mere germs, but they are germs with a "potential" value, 

 and are, as it were, the roots of growths which could not have 

 arisen without the previous establishment of the roots. 



Probably there may be other cases when the roots will be 

 found " sprouting " and giving rise to growths which are of com- 

 paratively slight functional use. Such may be the case with those 

 Cetacea which I saw, in which the baleen was present fairly 

 developed, but still in a minor degree. 



May I ask whether the palatal papilla? are really present in 

 all mammalia ? 



PROFESSOR FLOWER TO THE DUKE OF ARGYLL 



ROYAL COLLEGE OF SURGEONS OF ENGLAND, 



LINCOLN'S INN FIELDS, W.C., 



July 2, 1883. 



I do not think that it would be correct to say that the " palatal 

 papillae " are really present in all mammalia, as the palate is some- 

 times quite smooth. But the tissues of which they are formed 

 are there. 



In the rough diagram I enclose the red part represents the 

 vascular membrane covering the bone of the palate, corresponding 

 to, and in fact continuous with, the true skin, derm or corium, 

 which covers the external surface of the body. The blue is the 

 non-vascular epithelial layer, corresponding to the epidermis of the 

 surface, which is modified into nails, hair, horns, etc., in particular 

 regions. 



In No. i the surface is smooth. In No. 2 small ridges (there 

 seen in section), as in the human palate, are shown. In No. 3 



