160 Dr. W. Kiikenthal on the Adaptation of 



stronger. Precisely similar relations are found in Halicore 

 dugong. A large embryo, 5 feet 4 inches long, described by 

 Turner *, shows, besides isolated silky hairs arranged in rows 

 and more numerous on the head and trunk than on the limbs, 

 follicle-mouths closely packed between these, belonging to 

 very fine hairs which have not appeared. 



It follows that there can be no doubt that the Sirenians 

 have sprung from animals with a thick covering of hair. 



A precisely similar hairy covering is also found in the 

 hippopotamus f. While old specimens possess thick bristles 

 upon the upper and under lip, which become sparser on the 

 dorsal surface of the head and trunk, the skin of the head 

 and neck of a new-born animal exhibits a tolerably thick coat 

 of lanugo-like hairs, which therefore subsequently disappear. 

 But the whales also show vestiges of a former hairy coat, and 

 in this respect the Balsenoidea are most noticeable ; even in 

 adult animals solitary stiff bristles are still to be found in 

 the cephalic region. 



In a rorqual {Baloenoptera musculus) 62 feet long I found 

 at the tip of the lower jaw a triangular patch, 15 by 6*5 

 centim., of regularly arranged pits, which are to be regarded 

 as the remains of hair-follicles. These pits, which were about 

 2 millim. broad and 1 millim. deep, were disposed in about a 

 dozen rows, the longest of which contained twenty- six pits. 

 The terrestrial ancestors of the whalebone whales therefore, 

 besides having a coat of hair over the whole body, also 

 possessed a thick tuft of vibrissa? upon the chin, much in the 

 same way as the walrus or the bearded seal bear them on both 

 sides of the upper lip in front. Embryos of the latter animals 

 exhibit areas of pits in this region, just as regularly arranged 

 as in the adult rorqual. 



On the body of the same rorqual I found scattered hairs 

 arranged as follows : — On the upper jaw they stood in rows 

 close to the mouth ; nearer the dorsal region they got more 

 irregular, and disappeared behind the blow-hole. The lower 

 jaw likewise possessed hairs arranged in three rows lying one 

 above the other on each side ; those of the lowest row in 

 particular were surrounded by rings of pigment about the size 

 of a cherry. The distance between each hair was about 

 1 foot. 



Nearly all these brittle hairs, which were about one inch in 



* Turner, " On the Placentation of Halicore dugong ? Trans. Roy. Soc. 

 Edinb. vol. xxxv. part 2 (1889). 



t Vide Weber, " Ueber die Ilaut von Hippopotamus ampldbius? Studien 

 iiber Saugethiere, Jena, 1880, p. 3. 



