6^ 



Catotlon or Eupliysetes) wliicli is nearly, as we have seen, tlie 

 same as a porpoise in all the essentials of its structure, is rendered 

 comparatively harmless by the want of teeth in the upper jaw. 

 This deficiency perhaps was necessary to aid its bulky stores of 

 spermaceti in balancing the specific gravity of its massive skull. 

 Eight whales are in like manner rendered mild and timid by an 

 entire want of teeth, although the weight of their skull is also 

 relieved by the peculiar way in which the quantity of bone in it 

 is reduced.* Thus it is that immense size is not ordinai'ily the 

 characteristic of a beast of prey, and that the largest Getaceaiee,^ 

 only on minute mollusca. As for the immense size of Cetacea, it 

 evidently proceeds from their buoyancy in the medium in which 

 they live, and their being enabled thus to counteract the force of 

 gravity. 



Sperm whales are found to inhabit warmer seas than true 

 whales, and are brought more within the reach of those persons 

 Avhose love of destruction is attracted by their size and timidity, 

 and whose love of money is excited by the value of their oil. 

 Many whalers of late have declared that the number of young 

 sperm calves annually killed is so great as to threaten the speedy 

 annihilation of this kind of whale. With less motives for killing 

 off the species, thus certainly within our own times has man 

 wantonly extinguished the Nestor productus of Phillip Island, and 

 probably, at an earlier date, occasioned the similar fate of the 

 singular Dodo. 



But while we may regret the premature extinction of a harm- 

 less and useful species of animal by the destructiveness of another 

 one, there can be no doubt that the creator has imposed a natural 

 limit to the duration of every species on the surface of this globe. 

 Just as individuals are born into the world, live, and, after an 

 appointed period, die ; so we are taught by geology, that the 

 time of the natural existence of every species is also limited. 

 "We observe the first appearance of a species of animal in one 

 stratum, we view it flourishing, as it were, in another, that 

 we trace it languishing, and its numbers rapidly decreas- 



* It is for a similar reason that so many dolphins aiid other Cetecea have 

 the branches of their under jaw hollow, while the symphysis is very sliort. 



