60 GENERAL ORNITHOLOGY. 



What is a Bird? — There is every reason to believe that a Bird is a greatly modified 

 Reptile, being the otispring 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 tlie period of the world known to human history. There is no 

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

 now possesses ; bnt that every bird now living is the naturally modified 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 from such birds as are now living. This is 

 the Darwinian logic of observed facts, ujion which the modern Theory of Evolution is based, 

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

 has no scientific basis whatever, and is consequently accepted as true by few thoughtful per- 

 sons who are capable of forming independent judgments. Accordingly, 



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

 such important structural characters, that we unite the two classes, Aves and Eeptilia, in one 

 primary group of Vertebrata, or animals with a backbone. This group is called Sauropsida, 

 or reptiliform ; it is contrasted, on the one hand, with Ichtliyopsida, or fish-like vertebrates, 

 including Batrachians as well as Fishes; and, on the other, with Mammalia, the province of 

 Vertebrata which iucludes Man and all other animals that suckle their young. We find that 



Sauropsida (Gr. a-avpos, sauros, a reptile; o-^n, opsis, appearance), or lizard-like Ver- 

 tebrates, agree with one another, and difi'er from other animals, in the fidlowing important 

 combination of characters, substantially as laid down by Professor Huxley — some of the char- 

 acters being shared by Ichtliyopsida, and some by Mammalia, but the sum of the characters 

 being distinctive of Sauropsida : They are all oviparous (laying eggs hatched outside the body 

 of the parent), or ovoviviparous (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 a 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 coine together 

 behind in a common receptacle, the cloaca, or sewer, 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 thorax, 

 or chest, by a complete muscular partition, or diaphragm. The two lateral hemispheres of 

 the brain are not connected by a transverse commissure, or corpiis callosum. 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 three or four separate chambers — four in birds, in 

 which the circulation of hot blood is completely double, i. e., in the lungs and right side of the 

 heart, in the body at large and left side of the heart. The aortic arches are several ; or if but 

 one, as in adult birds, it is the right, not the left as in Mammals. The centra, or bodies, of 

 the vertebrae are ossified, but have no terminal epiphyses. The skull hinges upon the back- 

 bone by a single median protuberance, or condyle, and tlie basioccipital part bearing the con- 

 dyle is completely ossified. The lower jaw, or mandible, consists of several separate pieces, 

 the articular one fif which hinges upon a movable quadrate bone; and there are other pecu- 

 liarities in the formation of the skull. Tiie ankle-joint is situated, not, as in Mammals, be- 

 tween the tarsal bones and those of the leg, but between two rows of tarsal brnes. The skin 

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

 living members of the class of Birds from any known Reptiles, the characters of the two groups 



