Page:The American Cyclopædia (1879) Volume XI.djvu/89

 MAMMALIA 81 I a second repetition of the third ; and 10, quadrumana, having relations with man. The fundamental idea of the classification of Eitzinger (1843) is the same as that of Oken, the class mammalia having five series, accord- ing to the development of the organs of sense, and each series three orders, viz. : TOUCH. TASTE. SMELL. Cetacea. Pachydemnata. Edentata. 1. Balanodea. 1. Phocina, 1. Monotremata. 2. Delphinodea. 2. Obesa. 2. Lipodonta. 3. Sirenia. 8. Ruminantia. 3. Tardigrada. HEARING. VISION. Unguiculata. Primates. 1. Glires. 1. Chiropteri. 2. JSrutfi. 2. Hemipitheci. 8. Ferae. 8. AnthropomorpJii. Of the embryological systems of classifica- tion may be mentioned those of Von Baer, Van Beneden, and Vogt. Von Baer (1828) proposed the following divisions of this class )f his doubly symmetrical or vertebrate type, with osseous skeleton, lungs, an allantois, and an umbilical cord: the cord may disappear early, 1, without connection with the mother (monotremata), or 2, after a short connection with the mother (marsupialia) ; or the cord may be longer persistent, 1, the yolk sac con- tinuing to grow for a long time, the allantois growing little (rodentia), moderately (insec- tivora), or much (carnivora), or 2, the yolk sac increasing slightly, the allantois growing little and the umbilical cord very long (mon- keys and man), continuing to grow for a long time and the placenta in simple masses (ruminants), or growing for a long time and the placenta spreading (pachyderms and ceta- ceans). According to Vogt (1851), mammals may be arranged in two divisions: I., aplacen- taria, with the orders monotremata smd^mar- supialia; and II., placentaria, with series 1, composed of the orders cetacea, pachyder- mata, solidungula, ruminantia, and edentata ; series 2, of the orders pinnipedia and carni- vora ; and series 3, of the orders insectivora, volitantia, glires, quadrumana, and bimana. Van Beneden (1855), in the class mammalia of his hypocotyledones or hypovitellians (ver- tebrates), in which the vitellus or yolk enters the body from the ventral side, establishes the orders primates, cheiroptera, insectivora, ntia, carnivora, edentata, proboscidea, un- ilata, sirenoidea, and cetacea. Prof. Baird in vol. viii. of the "Pacific Railroad Survey," 1857) adopts the following arrangement: A, inguiculata, with the orders: 1, quadrumana ; cheiroptera; 3, rapacia ; 4, marsupialia; rodentia ; and 6, edentata; B, ungulata, rders : 10, pinnipedia ; and 11, cetacea. ill of these, except the first, are found in forth America; the horse, though not now asting native, was formerly an inhabitant of lis country. Agassiz, in his essay on classifi- ition (1857), makes mammals the eighth class of vertebrates, with only the three orders of marsupialia, herbivora, and carnivora. Owen (in the article "Mammalia" in the "Cyclopae- dia of Anatomy and Physiology," 1847) admits in the sub-class of placentalia the ten orders of bimana, quadrumana, cheiroptera, insecti- vora, carnivora, cetacea, pachydermata, rumi- nantia, edentata, and rodentia, and in the sub-class implacentalia the orders marsupialia and monotremata; the monkeys by the galeo- pithecus are connected with the cheiroptera, and by the lemurs with the carnivora; the last by otaria are related to cetacea, which in turn have certain affinities with the fishes; the rodents are connected with ruminants by the musk deer ; the monotremata lead to rep- tiles. Before introducing the more recent classification of mammals by Prof. Owen, ac- cording to the cerebral system, the reader should be reminded that until the time of Cuvier the principal subdivisions were based upon the Aristotelian characters derived from the organs of locomotion, the secondary groups being established on the peculiarities of the dental system; Cuvier added others drawn from the osseous and generative systems ; De Blainville in 1816 first adopted the division, according to the method of reproduction, into monodelphs, didelphs, and ornithodelphs, or or- dinary mammals, marsupials, and monotremes, retaining for the most part the Linnsean or- ders. Classification by the placenta seems to have been first proposed by Sir Everard Home, but, as modified by successive naturalists, leads to many unnatural affinities ; placing, for, in- stance, rodents and insectivora with monkeys, and solipeds, pachyderms, and some ruminants with the carnivorous cetaceans. Prince Bona- parte, in his Sy sterna Vertebratorum (1840), adopts the division of placentalia and impla- centalia, subdividing the first into the sub- classes of educabilia and ineducabilia, the lat- ter including the orders bruta, cheiroptera, in- sectivora, and rodentia, with the common char- acter of a single-lobed cerebrum ; Prof. Owen regards this as the most important improve- ment since the establishment of the natural character of the ovo-viviparous or implacental division. In 1845 Isidore Geoffrey Saint-Hi- laire raised the marsupials to the rank of a distinct class, making its subdivisions orders equivalent to those of the placentalia; Owen, however, did not regard them as groups of equal rank and value. In 1849 Prof. Owen, from the consideration of the times of forma- tion and the succession of the teeth, divided mammals into two groups, monophyodonts, or those which generate a single set of teeth (as the monotremata, bruta, and cetacea), and the diphyodonts, or those which generate two sets of teeth (comprising the great bulk of the class) ; at the same time he wished it to be clearly understood that this dental character is not so associated with other organic charac- ters as to indicate natural or equivalent sub- classes. As early as 1842 he drew attention