60 GENEBAL OBNITHOLOGY. 



What is a Bird? — There is every reason to Relieve that a Bird is a greatlj' modified 

 Reptile, being the offspring by direct descent of some reptilian progenitor; and there is no 

 reason to suppose that any bird ever had any other origin than by due process of hatching out 

 of an egg laid by its mother after fecundation by its father, — just what we believe to have been 

 the invariable method during the period of the world known to human history. There is no 

 reason to believe that any bird was ever originally creiatexi and endowed with the characters it 

 now possesses ; but that every bird now living is the naturally modifl.ed lineal descendant 

 of parents that were less and less like itself, and more and more like certain reptiles, the 

 further removed they were in the line of avian ancestry frojn such birds as are now living. 

 This is the Darwinian logic of observed facts, upon which the modem Theory of Evolution is 

 based, in opposition to the tradition of the special creation of every species of animal ; which 

 latter has no scientific b&siis 'whatever, and is consequently a,ccepted as true by fe* thought- 

 ful persons who are capable of foifming itidependfent judgments. Accordingly, 



Birds and Reptiles — even those of the present geologic epoch — share so many and so 

 important structm'al characters, that the chiefs of science of our day are wont to unite the two 

 classes, Aves and ^pUlia, in one primary group of the Yertebrata, or anim&ls with a back- 

 bone. This group is called Sawopsida, or reptiliform ; it is contrasted, on the one hand, with 

 Ichthyopsida, or fish-Uke vertebrates, including Batrachians as well as Fishes ; and, on the 

 other, with Mammalia, the province of the Vertebrata which includes Man and all other 

 animals that suckle their young. We find that 



The Sauropsida (G-r. advpos, saWros, a reptile; Si//-ts, tipsis, appearance), or lizard-like 

 Vertebrates, agree vidth one another, and differ from other animals, in the following important 

 combination of characters, substantially as laid down by Professor Huxley, ^^ some of the char' 

 acters being shared by the tbhihyOpsida, and some by the l^amnultlm, but the sum of the 

 characters being distinctive of Bambpsida : They are all oviparous (laying eggs hatched out- 

 side the body of the parent), or ovovivipafous (laying eggs hatched inside the body of the 

 parent), being never viviparous (bringing forth alive young nourished before birth by the 

 blood of the mother). The embryo develops those foetal organs called amnion and allantois, 

 and is nourished before hatching by the great quantity of yolk in the egg. There are no 

 mammary glands to furnish the young With milk after birth. The generative, urinary, and 

 digestive organs come together behind in a common receptacle, the cloaca, of sevirer, and their 

 products are discharged by a single orifice. The kidneys of the early embryo, called Wolffian 

 bodies, are soon replaced functionally by permanent kidneys, and structurally by the testes of 

 the male and the ovaries of the female. The cavity of the abdomen, or belly, is not separated 

 from that of the thoras, or chest, by a complete muscular partition, or didphragm. The great 

 lateral hemispheres of the brain are not connected by a transverse commissure, or corpui 

 callosiMn. Air is always breathed by true lungs, never by gills. The blood, which may be 

 cold or hot, has red oval nucleated corpuscles; the heart has either tliree or four separate 

 chambers, — the latter in birds, in which the circulation of the hot blood is completely double, 

 i. e., in the lungs and one side of the heart, in the body at large and the other side of the heart. 

 The aortic arches are several ; or if but one, as in birds, it is the right, not the left as in rnam- 

 mals. The 'cmtta, or bodies, of the vertebra are ossified, but have no terminal epiphyses. 

 The skull hinges upon the back-bone by a single median protuberance, or condyle, and the 

 part bearing the condyle is completely ossified. The loWelr jaw consists of several separate 

 pieces, the articular one of which hinges Upon a moVa,ble quad/rate botle ; and there are 

 other peculiarities in the formation of the skull. The ankle-joint is situated, not, as in 

 mammals, between the tarsal bones and those of the leg, but betweeh two rows of tarsal bones. 

 The skin is usually covered with outgrowths, in the form of scales or feathers. — Different as 



