240 



THE SEALS. 



well fastened to the end of the vertebral 

 column; but this whole region is likewise 

 mostly hidden in the flesh. The digits of 

 these limbs are long, but connected to form 

 oars like those of the fore-limbs. The skin 

 always projects beyond the nails, which 

 appear to be set on the back of the flippers 

 and are sometimes altogether wanting. 



The direction of the limbs is specially note- 

 worthy. The fore-limbs are directed obliquely 

 downwards. The palm of the hand is turned 

 in the direction of the axis of the body. 

 These limbs, in the ordinary seals especially, 

 show the position originally assumed by the 

 limbs in the embryos of all vertebrates, as 

 long as they retain the form of fin-like lobes. 

 The hind-limbs are directed so far backwards 

 that they continue the horizontal direction of 

 the vertebral column; and the sole of the foot 

 is turned towards the vertical median plane 

 of the body, the first digit forming the inferior 

 edge of the member. This arrangement of 

 the limbs, altogether embryonic in its character, 

 is retained more particularly in the common 

 seals. In the eared seals the limbs are more 

 slender, and the fore and hind paws or flippers 

 assume a somewhat different direction, which 

 seems to aim at placing the soles on the hori- 

 zontal plane of the ground. 



The dentition is distinguished from that of 

 the Carnivora by a greater variability in the 

 number of the incisors, and by a less degree 

 of specialization in the molars. The normal 

 number of incisors in the Carnivora, six 

 above and six below, is seen only in many of 

 the young animals; but in most cases this 

 number gets considerably reduced in the 

 adult, and often so much so that the incisors 

 are entirely absent. The outer incisor of the 

 upper jaw often resembles the canine in form, 

 but always remains smaller. The canines, 

 which are always present, attain an enormous 

 size in the upper jaw of the walrus, and are 

 very strong in the eared seals. With respect 

 to form there is no longer any difference 

 among the teeth that come after the canines. 



They always stand apart from one another, 

 and neither premolars nor molars, carnassials 

 nor tubercled teeth can be distinguished. The 

 first of these uniform molars is usually smaller 

 and has a less pronounced form than the 

 others. Often it has only a single root, while 

 the others have two; but there end the differ- 

 ences that can be pointed out in seals' molars. 

 But as regards the form which they present 

 in different animals there are pretty consider- 

 able variations. In general the crowns are 

 flattened on the sides and divided into several 

 .lobes, of which the middle one is most pro- 

 minent, while those at each side often form 

 sharp-pointed cusps. In other cases the teeth 

 are more rounded, and in that way form a 

 transition to the perfectly flat molars of the 

 walrus. But even in these examples of retro- 

 grade development of the carnivorous denti- 

 tion the lower jaw always shows an essential 

 carnivore character in the structure of the 

 joint by which it is attached to the skull a 

 joint in the form of a transverse semi- 

 cylinder. 



The body is mostly covered with a very 

 short thick downy fur, in which are set short 

 bristly hairs which never become wet. 



Among the features of the internal organi- 

 zation we would draw attention to the large 

 broad brain with numerous convolutions, as 

 well as to special modifications in the structure 

 of the vessels and the heart, by means of 

 which these animals are enabled to remain for 

 a long time under water without breathing. 

 The placenta is zonary as in the land carni- 

 vores. The teats are situated very far back 

 in the abdomen. 



The seals are remarkably social animals, 

 which live in all seas (sometimes in large 

 flocks), which can ascend pretty high up rivers, 

 and are even found in some basins now cut 

 off from the ocean, such as the Caspian Sea, 

 Lake Baikal, and the Sea of Aral. They are 

 unquestionably very intelligent animals, de- 

 voted to their comrades, their consorts, and 

 their young, animals which are prevented only 



