162 Dr. W. Kiikenthal on the Adaptation of 



bearded whales have not been exposed to the influence of 

 aquatic life so long as the others. 



A second and quite fundamental difference between the 

 integument of the two groups lies in the appearance in the 

 toothed whales of remains of a dermal armature *. 



A whale which inhabits Indian rivers, Neomeris phoccenoides, 

 exhibits on the dorsal surface a large number of plates, regu- 

 larly fitted to one another and each bearing a tubercle. 

 These closely adjoining plates form a long narrow area, 

 besides which plates still exist on the anterior margin of the 

 flippers and round the blow-hole. That we are here not 

 dealing with a casual malformation is shown by the embryo- 

 logy of the animal ; for in an embryo of this rare whale we 

 find in place of the dermal scutes, in precisely the same posi- 

 tion, tubercles which cover the body to the number of many 

 hundreds, and on its anterior portion are arranged in rows. 



It might here be asked, " Is this appearance ancestral or 

 something newly acquired?" Reasoning by analogy we 

 must decide in favour of the former. In the first place there 

 are a number of reptiles which are undergoing the loss of 

 their dermal armature in precisely the same way, e. g. lielo- 

 derma or Dermochelys, the rudiments of whose dorsal coat of 

 mail are found in the embryo as a number of longitudinally 

 disposed rows of tubercles ; secondly, palaeontology affords us 

 direct proof that the dermal armature of terrestrial ancestors 

 disappears through adaptation to a pelagic mode of life. We 

 must therefore regard the appearance described in Neomeris 

 as a dermal armature in process of degeneration. 



This conclusion coincides with the view that the group of 

 whales originated in fresh water. Platanista and Jnia also 

 have preserved certain tolerably general mammalian charac- 

 teristics f. 



In this way, too, certain recent statements are rendered 

 intelligible, according to which tubercles occur on the back, 

 in point of fact on the anterior edge of the dorsal fin, in 

 porpoises, the near allies of Neomeris. While the common 

 porpoise (P/wcosna communis) possesses only a single row of 

 such tubercles, they run in three rows along the dorsal fin of 

 another species (Phoccena spinipinnis) . In the porpoises 

 therefore we find the last vestige of that dermal armature 

 which is still so distinctly developed in Neomeris. 



One conclusion only is possible from what has been stated, 



* Kiikenthal, " Ueber Reste eines Hautpanzers bei Zahnwalen," Anat. 

 Anzeiger, 1890, no. 8, p. 2.37. 



f Cf. W. II. Flower, "Die Wale in Vergangenheit unci Gegenwart und 

 ikr wahrscheinlicher Ursprung," Kosrnos, Bd. xiii. 1888, p. 531. 



