i89i.] 



THE BRITISH NATURALIST. 



231 



will find remains of birds with teeth, birds with long reptilian tails, 

 wingless birds of gigantic size, and other curious forms of birds which 

 once existed, but which have no modern representatives, just as there 

 are modern birds of which we can find no trace in the fossiliferous 

 strata. He must also remember that his lifetime, nay all the centuries 

 of which we can be said to possess any documentary history, are but 

 as a second of time in the eternity which has passed. A little 

 experience will teach him that he can produce marked varieties from 

 a common stock, for instance, from the Rock Dove ( C. livia ) he can 

 produce in a comparatively short period of time, almost any form 

 or colour he may wish, and if such wonders can, in the lifetime of one 

 man, be produced by artificial selection what can, or rather what has 

 been produced by natural selection in the countless aeons that have 

 passed since the first protists swam in the seas of a bygone world. 



To come back to the question with which we started out, "What is 

 a bird," I trust that what has been said will have made it clear that 

 it is, firstly, an animal ; secondly, that it belongs to that great kingdom 

 of animals which we call vertebrate or backboned; thirdly, that it 

 belongs to that group of vertebrates which is called sauropsida, 

 because of its affinity to lizards ; fourthly, that it differs from all 

 existing reptiles in the possession of feathers, though probably m this 

 respect there have been m the past transitorial forms; fifthly, that it 

 differs from all existing reptiles in the temperature of the blood which 

 is. higher even than in mammals, though again probably ancestral 

 transitional forms forbid us asserting this to be, as between reptiles 

 and birds, a distinctive character. If nothing has been proved it is 

 likely that the difficulty of defining what a bird is has been made 

 abundantly evident. If anyone can favor me with a concise and 

 accurate answ^er to the question " What is a bird" I shall be grateful, 

 but I trust our time has not been wasted, that our conceptions of the 

 origin and affinities of birds have not been more hazy and that we 

 have had a glimpse of what is meant by the plasticity and antiquity 

 of age. 



112 Bewsey Road, Warrington. 



Ovarium of a Domestic Fowl.— A brown double combed domestic 

 fowl was hatched ist May, 1889, laid its first egg Jan. 7th, i8go, laid 

 January, February, March, April, and May, resting June and July, 

 and laying again through August, September, October, and November 



