IN THE LIMBS OF MAMMALIA. 47 



general plan of structure, may be intended to perform functions most diverse, and their out- 

 ward forms be in like degree modified. For instance, the fin-like flipper of the seal bears 

 little resemblance to the anterior extremity of the ape, and yet they are identical in their 

 general structure, — they are homologous. 



It may have been inferred, from what has been said above, that we have necessarily two 

 systems of nomenclature, according as morphology or teleology is taken as the basis. For 

 it is the latter which confers common and popular names on objects of Natural History, and 

 arranges them in a way which, though convenient enough under ordinary circumstances, 

 utterly fails of precision for all scientific purposes ; and the anatomist and zoologist soon 

 learn that morphology alone must be their guide in scientific nomenclature. Thus the 

 name fish is applied to several animals in structure very unlike the true Pisces, merely be- 

 cause, like that group of Vertebrates, they live in the water : to certain Radiates, as the 

 star-fish and sun-fish ; to Articulates, as the cray-fish ; and, formerly, even to the whale, an 

 air-breathing Mammalian Vertebrate. So among Articulates, the monosyllable fly forms the 

 ending of the common names of many insects, as butter-fly, dragon-fly, harvest-fly, ichneu- 

 mon-fly, members respectively of the sub-orders Lepidoptera, Neuroptera, Hemiptera, and 

 Hymenoptera, though it is only to the Diptera that the name fly properly belongs. 



These are zoological ambiguities ; anatomical ones are even more frequent. All organs 

 of aerial locomotion are commonly called wings, whether they are articulate or vertebrate 

 in type, or whether, within the latter group, they are avian or mammalian, as those of the 

 bats; and the same is the case with other parts and organs, thorax, abdomen, heart, liver, 

 and stomach. 



I could not well pass over this most important branch of the subject ; but the great ne- 

 cessity to the philosophical naturalist for a revised anatomical nomenclature has already 

 been strongly urged by Professor Agassiz, before the Boston Society of Natural History. 1 

 Premising that the members of the four great types have nothing in common beyond 

 their all being animals, and that, therefore, no parts, however similar in function, can pos- 

 sibly be homologous in animals belonging to any two of these types, he showed the propri- 

 ety of restricting the common names mouth, stomach, heart, and the like, to one of these 

 groups, the Vertebrates perhaps, and of applying other names to the analogous parts in the 

 other three types. Perhaps the change should be even greater than this ; for, since these 

 new names would of course be classical in their derivation, and the common ones, though 

 scientifically restricted, would in general discourse retain the same loose application, it 

 would seem better to employ new terms for the various parts and organs in each of the 

 four types, leaving the common ones as they are now. It is evident that much remains to 

 be done in this matter of anatomical nomenclature, and that it is of as much importance to 

 the anatomist as are the names of the animals themselves to the zoologist. 



Popular descriptive zoology concerns rather the teleological characters of animals, while 

 the strictly scientific and systematic arrangements are based upon anatomy, and thus upon 

 morphology. 



We have noticed one distinction between the terms given above : that morphology and 

 homology both refer to structure, while teleolog} 7 and analogy both refer to function. Affin- 

 ity is merely a common synonjm for homology, and ma} r therefore be omitted. And now 

 the four principal terms pair off on another basis ; morphology and teleology are absolute 

 terms, as it were, and may refer to the structure or the function of but a single part or organ ; 



1 See also his section on Morphology and Nomenclature, in Contributions to the Natural History of the United States, 

 vol. iii. chapter ii. section iv. ; also section iii. p. 69. 



