66 



FIRST CLASS OF THE VERTEBRATED ANIMALS. 



together all the known species of this genus, and then taking the mean of their di- 

 mensions, M. Isidore Geoffiroy found that the largest species only eKceeded this mean 

 by an inch and a quarter, while the smallest remained bolow the average by an equal 

 ■quantity. If, however, the Ouistitis be subdivided into those three sections usually 

 received by Naturalists, then the dimensions of the species belonging to each section 

 will differ from the medium magnitude proper to that section only by six lines one 

 «ay or another. 



Axrtong the Bats the genus Vespertilio, as formerly established, would seem at 

 first sight to present a striking exception to this rule, in respect to the Roussettes, 

 in which the distance between their expanded wings is four feet, while the smaller 

 species of this country scarcely measure as many inches. But upon investigating the 

 characters upon which the genus had been instituted, M. Geoffroy observed several 

 important points of difference between the organization of the larger and the smaller 

 Bats, which have ultimately led to their being separated into distinct subdivisions and 

 genera. IVIany other apparent exceptions have also vanished in a similar manner on 

 being examined more minutely, and the consequence has been, that several new 

 Genera have been adopted by the general consent of Naturalists. Indeed, it may be 

 stated generally, that wherever thei-e have existed striking differences of size between 

 nearly-allied species, Naturalists have always felt the necessity of establishing sub- 

 genera, or groups in which these remarkable anomalies are made to disappear. 



Since it thus appears that the sizes of the Mammalia bear a determinate relation 

 to those external characters which usually serve to determine the Genera or higher 

 divisions, it will follow that their magnitude must bear a corresponding relation to 

 the conditions of their existence, such as the element in which they move, theu* mode 

 of Ufe, their food, their climate, and their situation. In all these respects we may 

 expect to find that their sizes will be so apportioned by Nature, as to bring them into 

 harmonious correspondence with the circumstances of their condition. 



In reference to the element in which they move, we find that all those Mammalia 

 which dwell in the bosom of the ocean acquire the largest dimensions. The different 

 sfiecies of VVliale (Balana), of Cachalot CFhi/seler), and of Dolphin {Delphinus)y 

 attain a bulk to which few other Mammalia can compare. Even among those groups 

 of Mammalia where some genera commonly frequent the water, and others live habi- 

 tually on the land, we find that the former attain to a magnitude much greater than 

 that of the latter. Thus, among the Carnassiers, no species reaches so great a size 

 as the Sea-Horse or Morse (Trickechus rosmarus). Again, among the numerous 

 animals composing the Genus Mustela of Linnaeus, the Weasels, Martins, and other 

 terrestrial species, are much smaller than the Otters. Even among the Otters 

 (^Lutra), it is precisely those species which are the most essentially aquatic, such as 

 the Brazilian Otter (Z*. Braziliensis), and the Sea-Otter (X. lutris), which attain 

 the greatest dimensions. The same observation is also applicable to the Rodentia 

 and Insectivora. The Beaver is larger than the Mouse, and the Water Shrew {Sorex 

 Jodiens) of greater magnitude than the common Shrew (5*. araneus), and for a si- 

 milar reason. This adaptation of Nature seems obviously intended to accommodate 

 their bodies to the density of the medium in which they more habitually reside. A 

 greater bulk, by displacing a larger quantity of water, renders them more buoyant, 

 and leaves the muscular force of their limbs more unfettered to execute the movements 

 proper to each animal. Again, the force of gravity at the earth's surface being 

 counteracted in a more sensible degree by the reaction of the denser fluid, enables 

 some of the aquatic species to attain a bxdk which would be impossible in a land 

 animal. 



On the other hand, those Mammalia which hve more exclusively in the air, such 

 as the Bats, or upon trees, like the greater part of the Monkeys, never attain any 

 very considerable dimensions. The agility which their situation requires would have 

 been inconsistent with a heavy form, and the dimensions of the trees in which most 

 Quadruraana fix their abodes, necessarily confine their magnitude within very nar- 

 row limits. Among the remaining Mammalia which commonly live on the surface 

 of the land, and may thence be more particularly denominated terrestrial Mammalia, 

 we find that their average bulk maintains a size intermediate to these lighter forms 

 of the aerial Mammaha on the one hand, and those belonging to the more ponderous 

 inhabitants of the ocean on the other. The relative magnitude depends, however, 

 with the terrestrial Mammalia, upon cerfain other conditions; for, while we find some 

 animals among them which only yield in magnitude to the aquatic tribes, we at the 

 same time discover in this division the very smallest animals of the entu-e class with- 

 out exception. This rule, therefore, does not hold so accurately in respect to those 

 animals which dwell habitually on the ground. 



If, however, we investigate the terrestrial and aerial Mammaha in reference to the 

 nature of their food, we find certain constant relations estabhshed by the Creator between 

 the quantity of food necessary for their maintenance and that which is supplied to them ; 

 in other words, between the demand of their stomachs and the supply of food suffi- 

 cient to sustain them. The largest of all terrestrial Mammaha are the Herbivorous 

 animals, such as the Elephant, Hippopotamus, and Rhinoceros, because the grosser 

 kinds of ve^^etable food are supplied in immense quantities throughout many parts of 

 the globe, but especially in the tropical chmates. The warmer regions of the globe 

 yield, in a dense and luxui'ious vegetation, an ample supply of nourishment to these 

 ponderous frames; and supply those succulent plants, soft stems, and leaves, the 

 want of which renders the regions around the poles wholly incapable of supporting the 

 larger terrestrial Mammalia. In the group of Herbivorous Mammaha, while we have 

 the colossal magnitude of the Elephant on the one hand, we have on the other the 

 Java Musk (Moschus memlnaj, scarcely the size of a Rabbit. 



The Carnivorous Mammalia compose a group which forms, after the preceding, a 

 • series of an inferior order. Among them we have the Lion and the Tiger for the 

 maximum, and find a minimum limit probably in the Ermine (Mustela erminea). 

 Althou"-h these animals find an abundant supply of nourishment among the inferior 

 tribes of every denomination, it is neither so ample nor so constant as to permit them 

 to attain any very great dimensions. An unwieldy bulk would ill correspond with 

 that activity which their predatory habits seem necessarily to require. 



The Frufrivorous tribes of Blammalia form a third group confined within much nar- 

 rower dimensions. On the one hand we have the OrangSj and on the other the 



smallest species of Roussette Bats (Pteropus). These species are accordingly con- 

 fined to those more favored regions of the earth, where fruits are to be found 

 throughout all seasons of the year. 



Lastly, we see among those Mammalia which feed exclusively on Insects a further 

 instance of the relation which the nature of the food bears to the average bulk of 

 species. While we have the Ant-eaters (Myrmecophaga and Orycteropus)^ whose 

 length does not exceed four feet, we have, in the minute Shrews, some of the smallest 

 of known Quadrupeds. 



Thus, upon considering all the Mammalia, in a general point of view, in reference 

 to their comparative dimensions, we are led to perceive that there always exists a re- 

 lation between the bulk of the animals composing an entire group and the conditions 

 of their diet. The more capacious animals feed upon those substances which are 

 found most abundantly on the face of the globe. Those of smaller size usually attain 

 to dimensions proportional either to the magnitude of the animals upon which they 

 are destined to feed, or to the nature of those vegetable substances to which their 

 digestive organs are adapted. Every where we perceive a most exact correspondence 

 between the quantity of nourishment which their constitution requires, and that which 

 is bestowed by the hand of Nature. This method of apportioning to each animal, by 

 an equitable division, its share of the produce of the earth, is surely one of the most 

 admirable and beneficent arrangements of the Creator. 



Although the subject of the Geographical distribution of the Blammalia will here- 

 after receive our most attentive consideration, it may be proper to remark at present, 

 that the dimensions of animals always bear a certain relation to the magnitude of the 

 regions in which they reside. It has long been remarked, that islands which are 

 either very small or much isolated contain very few Quadrupeds, and those only of 

 small dimensions, while some are even wholly destitute of Mammalia. Indeed, the 

 largest animals of this class are found only upon the continents, in the largest islands, 

 or upon those smaller islands which are so near to the larger continents as to be inti- 

 mately affected by their proximity. Even in respect to the continents themselves, 

 the Mammalia belonging to the Old Continent, which is the larger, surpass in dimen- 

 sions those of the American, which is the smaller. The Mammalia of New Holland 

 come next in magnitude, then those of Madagascar, Britain, and the lesser islands. 

 A similar law may be traced among the aquatic Mammalia, for those which inhabit 

 the Ocean greatly surpass in bulk the species that frequent the Rivers. The lart'est 

 of the latter do not exhibit Mammalia which can be compared in any degree with the 

 Morse and the Basque Whale. 



Thus, whether we investigate the Land or the Sea, every where we perceive that 

 the dimensions of the Blammalia are proportioned to the magnitude of the regions 

 which they are destined to inhabit. If the Southern hemisphere be compared, as a 

 whole, with the Northern, omitting Africa and those islands which are traversed by 

 the Equator, as the animals must be nearly the same on both sides of this line, we 

 shall find that the Southern hemisphere will contain Mammalia whose size is gene- 

 rally less than that of the corresponding animals in the North. This is, however, 

 only a particular case of that more general law already explained, for the Southern 

 hemisphere contains at most only small continents or large islands. 



Differences of latitude and climate lead to many important corresponding differences 

 in the sizes of animals, but these do not admit of being expressed in a general law 

 but must be noticed in detail. It most commonly happens that genera and species 

 arrive at their maximum of size in the hottest regions of the globe, and descend to 

 their minimum in the coldest. There are, however, some Mammalia, such as the 

 Bears, which have their maximum in the Polar Regions, while their cono-eners of 

 the tropics are greatly inferior in bulk and strength. But there is no instance in 

 any one genus where the largest species are found alone in temperate or moderately 

 warm climates ; and the same observation is equally applicable to the several indivi- 

 duals of the same species. 



It commonly happens, when individuals belonging to the same species inhabit both 

 the mountains and the valleys, that the inhabitants of the mountains will be the 

 smaller of the two groups. This probably arises from exposure to cold, and a scanty 

 supply of food. Here again we find that correspondence between the dimensions of 

 the animals and those active habits which a mountain residence demands. A heavy 

 and unwieldy form would have been unsuited to the difficulties of those almost inacces- 

 sible heights, where the mountain races are often compelled to gather a scanty and 

 precarious subsistence. 



Among the domestic animals, individual variations of height happen very rarely, 

 and are commonly confined within narrow limits, while, on the contrary, the varia- 

 tions in the dimensions of races are sometimes both very numerous and remarkable. 

 With some domestic animals the primitive height of the wild species is preserved, or 

 it has been very slightly modified. In these instances all the races have the same 

 height, or differ very slightly ; and whenever they are found to vary from the height 

 of the wild races, it is always to become a little smaller. 



There are some species of domestic animals, such as the Dog and the Horse, 

 which present some races of very large dimensions, and others, on the contrary, are 

 very small. "N^Tien, however, the medium height of all the races is ascerta-ned, it 

 is found to differ but slightly from the height of the original type, as deduced from 

 measurement or from reasoning. Thus the ordinary height of those species which 

 vary but slightly, as well as the medium height of all the races of those species which 

 vary much, approach very nearly to the dimensions of the height belonging to the 

 primitive type. In other words, species have vai-ied but slightly ua their average 

 dimensions from the time when they were first domesticated. 



There are certain lesser variations in dimensions, which depend upon the greater 

 or less care which the individuals receive on the part of Man. Those species which 

 have experienced a slight diminution, belong to such as have been generally neo-lected 

 or badly nourished. * 



The predominance of the Blale over the Female in dimensions is much more 

 general, and more strongly marked among the Mammalia than among the Birds, or 

 in any other class. There is a remarkable disproportion between the size of the 

 Bull and that of the Cow ; of the Ram and the Ewe ; and of the He and She Goat. 

 This superiority of volume is not, however, essential to the male sex ; and far from 



