152 



KNOWLEDGE 



[August 1, 1892. 



fauna and flora of Madagascar, though showing African 

 affinities, is remarkable for the extraordinary differences 

 which exist between it and that of the continent opposite. 

 Hence, Mr. Wallace concludes that it was severed from 

 Africa before that continent received its present character- 

 istic assemblage of plants and animals, which apparently 

 migrated into it from more northerly parts. Madagascar 

 is thus regarded as having preserved its lemurs, tanrecs, 

 and other peculiar animals, as relics from a time dating 

 back at least to the Miocene period, before Africa itself had 

 received the baboons, antelopes, hi^jpopotamus, &c., which 

 now distinguish it, but which are absent from Madagascar. 



The Sandwich Islands form a good type of the third 

 division, that of oceanic islands, which have never been 

 connected with any continent at all, but have been formed, 

 usually either as volcanoes or coral islands in mid-ocean. 

 In such cases we of course find no indigenous land 

 mammalia, since there would be no means for their con- 

 veyance thither, and whatever forms of life the islands have 

 received may be expected to have come from various 

 quarters, the winds and ocean currents being the chief 

 means of their introduction. Hence we find a somewhat 

 mixed assemblage, showing no close conformity to those of 

 any one particular continent. The flora of the Sandwich 

 Islands is very rich and extremely peculiar, there being, 

 out of 70.') flowering plants, no less than 574 which are 

 quite peculiar to the islands. Some of these, belonging to 

 genera which in other parts of the world are low herba- 

 ceous plants, attain the dimensions and habit of shrubs, 

 and even sometimes of trees ; such is the case with 

 certain lobelias, violets, and composittp. 



In connection with New Zealand a most interesting 

 sketch is given of probable geological and geographical 

 changes in the remote past, by which Mr. "Wallace proposes 

 to explain the peculiar and puzzling character of the present 

 flora and fauna of the islands. According to this theory 

 New Zealand received the ancestors of its recently extinct 

 gigantic wingless birds, the moas, and of the present 

 rapidly disappearing apteryx or kiwi, by a connection with 

 north-eastern Australia, while that part of the island was 

 still unconnected with its western half, and had not yet 

 received its characteristic marsupial fauna, a route by 

 which also it received that part of its flora which is tropical 

 in character. Recent information as to soundings round 

 New Zealand, and the discovery of fossil tertiary and 

 cretaceous plants in both New Zealand and Austraha, 

 enable the argument here to be more fully elaborated than 

 was possible in the former edition. 



RUMINANTS AND THEIR DISTRIBUTION. 



By R. Lyuekker, B.A.Cantab. 



FROM early times we find the function of ruminating, 

 or " chewing the cud," recognized as a peculiarity 

 of the group of mammals known in semi-popular 

 language as ruminants. Thus in Deuteronomy 

 the animals permitted for food are those that 

 " chew the cud and part the hoof" ; while the swine " which 

 part the hoof but do not chew the cud " are forbidden. 

 On the other hand, the camel, which chews the cud but 

 has not paired hoofs, is in the forbidden list. In the per- 

 mitted animals we thus have a recognition of the group of 

 ruminants as represented by oxen, .<:heep, and deer; of 

 which no better short definition can be given than that 

 they chew the cud and have each foot furnished with a 

 pair of hoofs symmetrical to a vertical line between them. 

 The want of the paired hoofs in the camels, which are 

 also cud-chewers, shows, however, that these two 



characteristics will not hold good for the entire group. As 

 we proceed, we shall find that there are structural features, 

 common to the group, in addition to the peculiarity of 

 rumination ; but, before going further, we may observe that 

 the recognition of their paired hoofs, coupled with the 

 absence of rumination, is an exact statement of the rela- 

 tionship of the swine to the true ruminants. 



The word "ruminant" comesfromthe Latin rumen, which 

 was applied both to the "cud" and to that part of the 

 stomach in which the latter is contained previous to 

 chewing. The Greeks had a word iiwruhi, or nwrulnzo 

 (from memo, to revolve), to express this action of cud- 

 chewing, and a derivative from the former was used by 

 Aristotle to designate ruminants, who tlms first 

 distinguished the group by a definite name. This early 

 recognition of the ruminants as a group is probably due 

 to their importance to man, the Biblical record .showing 

 that they yielded the only mammalian food permitted to 

 the Hebrew, and this pre-eminence as a source of food has 

 scarcely decreased to the present day. They are, moreover, 

 now the dominant type of larger mammals, as witness the 

 herds of bison which lately roamed over the American 

 prairies, and the droves of antelopes on the African 

 " veldt." 



Commencing with the function of rumination, we may 

 observe that it is a re-mastication of grass or other 

 vegetable food, swallowed almost as soon as plucked, and 

 transferred to a special receptacle in the stomach. From 

 this, it is regurgitated into the mouth by a reversed action 

 of the muscles of the throat, and, after having undergone 

 mastication — or rumination — is transferred to the digesting 

 part of the stomach. Now, it is evident that this compli- 

 cated arrangement, so different from that of other animals, 

 must be of some special advantage to the ruminants. As 

 a matter of fact, these animals, like other large herbivora, 

 are obliged to consume a large quantity of food to obtain 

 sufficient nutriment ; and it is obvious that if this food had 

 to be masticated as soon as plucked, the operation of 

 feeding would be very protracted ; but by the arrangement 

 mentioned the requisite amount of food can be gathered 

 within a comparatively short time, and the animals can then 

 retire to ruminate in concealment. It is superfluous to com- 

 ment on the advantage this is to creatures which, Uke many 

 ruminants, have but little means of defehduig themselves 

 against carnivorous foes ; but we may mention that many 

 still further increase this advantage by feeding only at 

 dawn or evening, when they are far less conspicuous than 

 in the mid-day glare. There is, moreover, evidence that 

 when ruminants first appeared, this rapid feeding was of 

 more importance than at the present day, since while 

 many of the modern larger forms, like oxen, antelopes, and 

 deer, are provided with formidable weapons in the shape 

 of horns or antlers with whijh they can keep foes at bay, in 

 earUer times such weapons were either absent or but feebly 

 developed. Seeing, then, that the 



function of rumination is 

 correlated with a special 

 compartment of the stomach 

 for the temporary reception 

 of the freshly-gathered food, 

 it would be expected tbat 

 animals thus provided would 

 also possess an efficient mas- 

 ticating arrangement for re- 

 ducing their food to the condition in which it yields the fullest 

 nutriment. Such, indeed, is the case, the grinding-teeth 

 of ruminants being of a complex structure, unknown 

 elsewhere. In our previous article on " Teeth and their 

 Variations," we have indicated the characteristic structure 



Fig. 1. — The lirst upper molar 

 and last two premolars of a 

 Rinninaut. 



