ON THE GREENLAND RIGHT- WHALE. 83 



«dfes of the vipper jaw, characteristic of the older individuals of the species, but the same 

 form is also found in the skeleton of the very young Cape whale, described by Cuvier. 



That the oblique position of the lateral parts of the cranium can gradually diminish in the 

 Cape whale during the growth of the animal, while in the Greenland whale, on the contrary, it 

 becomes continually more distinct, can scarcely be explained except in connection with the 

 difference which, in these two right-whales, contemporaneously developes itself in the structure of 

 the anterior walls of the cranial cavity, and which therefore requires from us now a little attentive 

 consideration. 



Although the right-whales, like other Cetaceans, at their birth are generally in a greatly 

 advanced state of development, their skull, however, is at that time so little developed in its 

 structure that the primordial cranium of the already colossal head is still preserved to a great 

 extent. This is the case, even in the occipital bone, though in this the ossification is first 

 completed (see Plate III, fig. 1). This strangely retarded development of the skull of the 

 rio-ht-whales can by no means be accounted for by the supposition, that the brain itself grows 

 more rapidly than in the mammalia generally. One glance at the space of the cerebral 

 cavity of the full-grown animal will be sufficient to show that it is quite the reverse (Plate 

 V, fig. 1, a), for even absolutely speaking it is scarcely larger than that of the newborn 

 animal. The only cause of this retardation is, that in these animals the function of the skull, 

 as a receptacle for the brain, is, as it were, only secondary to its function as a support of the 

 upper jaw. Por this purpose the anterior wall of the cranial cavity is thickened to such a degree, 

 that a section through it in the mesial line of the Greenland whale cranium (Plate V, fig. 1), is 

 five times as large as the diameter of the cranial cavity itself. The anterior wall of the cranial 

 cavity does not, however, attain to this thickness by a corresponding increase of the frontal 

 bones alone, but also by that of the ethmoid, the anterior sphenoid, and the entire squamous 

 portion of the occipital bone, all which bones are combined to form the front wall of the cerebral 

 cavity. That the ethmoid forms part of this wall, may also be true, in speaking of most other 

 mammalia, as this bone, on account of the great development of the upper jaw, is quite commonly 

 raised from a horizontal into a vertical position on the base of the skull ; but the most that can 

 be said of the occipital bone is, that its squamous portion, on account of the greater develop- 

 ment of the upper jaw, may be placed far more forward on the superior surface of the skull, 

 and its articular portions farther upwards on the back of the head, by which means the occipital 

 foramen is removed farther backwards. It is peculiar to the Cetaceans for the squamous portion 

 of the occipital bone to be so far advanced on the superior surface of the skull, that the occipital 

 foramen itself is partially placed on this surface, and in the Greenland whales this peculiarity 

 is still farther developed, so that the whole occipital foramen is placed on the superior surface of 

 the head, and the squamous portion itself only covers an extremely small portion of the brain, 

 while it partakes to a great extent in the formation of that osseous mass, into which the front 

 wall of cerebral cavity is changed. The skull of the right-whales may accordingly be said to 

 develope itself very rapidly after birth, not, however, accommodating itself to a continued growth 

 of the brain, but almost entirely in relation to the increasing weight of the upper jaw. It not 

 only grows extraordinarily thick in the front wall of the cerebral cavity, but all its differ- 

 ent bones alter their relative positions. In this respect, the Cape whale, however, seems to be 

 very different from the Greenland whale. For in the former, the front wall of the cranial cavity is 

 raised very much during its growth, by which means the upper jaw gains considerably in height 



