332 ZOOLOGY. 



urally suggest themselves aud be answered. In the first place, of 

 course, orders, like every aggregation of animals and plants, must to 

 a large extent be arbitrary, and their relations have to be determined 

 by a certain standard, from which greater or less deviation must be 

 made in individual cases, according to circumstances. The standard, 

 however, as will be admitted by i)robably every rational zoologist, 

 should be a type that from its nature and relations may be readily com- 

 prehensible and appreciated by the greatest number, and in regard to 

 which there is general concurrence. Undoubtedly it is in the class of 

 mammals that we find such requisites present in the greatest degree. 

 Accei^tiug Linnaeus as the originator, pro tanto, of the idea connected 

 with the name order, we naturally look to his exposition of the mammal 

 group^s. We find that though there have been great deviations from 

 his applications since his day, the fundamental idea of the group, as it 

 exists in nature, has been accepted, and the efforts of subsequent zool- 

 ogists have been chiefly in the direction of refinement and definition. 

 There is now a general concurrence as to the orders recognizable in the 

 class of mammals, although some little difference as to details still pre- 

 vails. Taking the uiost comi)reheDsive ones, we have the Primates, 

 Carnivores, Ungulates, Cetaceans, Sirenians, Chiropters, Insectivores, 

 Eodents, and Marsupials. Now, inasmuch as several of these have 

 been subdivided, let it be assumed that no groups between which exist 

 greater morphological differences than those which differentiate the 

 orders, with their maximum limits, from those nearest of kin, shall be 

 regarded as less than orders ; and, on the other hand, that we shall not 

 distinguish as orders such groups as have at least less differences than 

 those se})arating, for example, the Anthropoid and Lemuroid Primates, 

 the Fissiped and Pinniped Carnivores, and the Perissodactyle and Arti- 

 odactyle Ungulates. From this startiug-point it will be in j)lace to ex- 

 amine a couple of systematic attempts published during the i^ast year. 

 One has been a new revision of the class of Birds ; another, a reiterated 

 classification of the Fishes. 



In all nature, among the major aggregates of s])ecies, there is not a 

 more natural and homogeneous group than that which naturalists unan- 

 imously have agreed to consider as a class under the name of Birds. 

 So like are all the living representatives of this group in all essential 

 details of their morphology, that between the extremes there certainly 

 exist less differences than those which separate the cetaceous from any 

 other order, and i)erhaps less even than those which separate the Anthro- 

 poid and Lemuroid Primates, or the Fissiped and Pinniped Carnivores. 

 Nevertheless, the last reviser of the class has admitted no less than 

 26 orders. If the proposition that the order of Mammals is a proper 

 standard be accepted, there can be no question but that differentiation 

 in the class of Birds has been carried to a most unscientific extreme. 



The opposite extreme has been displayed in the treatment of the 

 classification of Fishes, in part at least, but at the same time a like 



