8 



Professor Flower 



[May 25, 



blades are supported and bound together for a certain distance from 

 their base, by a mass of less hardened epithelium, secreted by the 

 surface of the palatal membrane or matrix of the whalebone in the 

 intervals of the lamellar processes. This is the " intermediate sub- 

 stance " of Hunter, the " gum " of the whalers. 



The function of the whalebone is to strain the water from the 

 small marine mollusks, crustaceans, or fish upon which the whales 

 subsist. In feeding they fill the immense mouth with water contain- 

 ing shoals of these small creatures, and then, on their closing the 

 jaws and raising the tongue, so as to diminish the cavity of the mouth, 

 the water streams out through the narrow intervals between the hairy 

 fringe of the whalebone blades, and escapes through the lips, leaving 

 the living prey to be swallowed. Almost all the other structures to 

 which I am specially directing your attention, are, as I have men- 

 tioned, in a more or less rudimentary state in the Cetacea ; the 

 baleen, on the other hand, is an example of an exactly contrary con- 

 dition, but an equally instructive one, as illustrating the mode in 

 which nature works in producing the infinite variety we see in animal 

 structures. Although appearing at first sight an entirely distinct and 

 special formation, it evidently consists of nothing more than the highly 

 modified papillas of the lining membrane of the mouth, with an exces- 

 sive and cornified epithelial development. 



The bony palate of all mammals is covered with a closely adhering 

 layer of fibrovascular tissue, the surface of which is protected by a 

 coating of non- vascular ej)ithelium, the former exactly corresponding 

 to the derm or true skin, and the latter to the epiderm of the external 

 surface of the body. Sometimes this membrane is perfectly smooth, 

 but it is more often raised into ridges, which run in a direction trans- 

 verse to the axis of the head, and are curved with the concavity back- 

 wards ; the ridges moreover do not extend across the middle line, being 

 interrupted by a median depression or raphe. Indications of these 

 ridges are clearly seen in the human palate, but they attain their 

 greatest development in the Ungulata. In oxen, and especially in the 

 giraffe, they form distinct laminae, and their free edges develop a row 

 of pointed papillae, giving them a pectinated appearance. Their epithe- 

 lium is thick, hard, and white, though not horny. Although the 

 interval between the structure of the ridges in the giraffe's palate and 

 the most rudimentary form of baleen at present known is great, there 

 is no difficulty in seeing that the latter is essentially a modification of 

 the former, just as the hoof of the horse, with its basis of highly 

 developed vascular laminae and papillae, and the resultant complex 

 arrangement of the epidermic cells, is a modification of the simple 

 nail or claw of other mammals, or as the horn of the rhinoceros is 

 only a modification of the ordinary derm and epiderm covering the 

 animal's body differentiated by a local exuberance of growth. 



Though the early stages by which whalebone has been modified 

 from more simple palate structures are entirely lost to our sight, 

 probably for ever, the conditions in which it now exists in different 



