OF EVOLUTION. 23 



with a complete pulmonary circulation operated by 

 a four-chambered heart, and with the anterior 

 appendages so modified as to permit of navigation 

 through the air ; the mouth is destitute of teeth, 

 a character which serves to separate it from 

 the greater number of other vertebrate animals. 

 This is our conception of a modern bird. But 

 what has been its earlier history ? I have 

 placed before you the figure of a remarkable 

 creature, known as the Archaeopteryx, only two 

 individuals of which have thus far been discov- 

 ered. The first, now deposited in the British 

 Museum, was found about twenty-five years 

 ago, and the second some ten years since, and 

 constitutes to-day one of the treasures of the 

 museum of Berlin. They were both found in 

 the lithographic-stone quarries of Solenhofen, 

 Bavaria, and in deposits that by geologists are re- 

 ferred to the Jurassic period of time. This remark- 

 able creature, which was of about the size of a 

 raven, had a generally bird-like head, but differing 

 from all modern birds, the head was supplied with 



