12 THE EVOLUTION OF THE UNIVERSE 



because it throws no light on the living machinery 

 (the embryonic machinery) which causes the varia- 

 tions at birth. Also, it may be true that new species 

 are often formed by sudden, large changes at birth; 

 though few instances of this are positively known. 

 However that may be, Darwin pointed out a truth, 

 and we now know that it was in some ways more far- 

 reaching than he thought. He was a biologist, and 

 was concerned only with living things. We know to- 

 day that this truth more or less embraces the entire 

 universe. 



What we call the ''universe" to-day is a collection 

 of, perhaps, 2,000,000,000 suns or stars, to which our 

 sun or star belongs. No one can possibly count 

 them, as the greater part of them are represented 

 only by very faint points of light on photographic 

 plates which have been exposed for many hours in 

 giant telescopes. They crowd together, making little 

 clouds of light on the plates; and we can merely 

 roughly estimate that there are about 2,000,000,000 

 of them in the system or collection to which our sun 

 belongs. No 'doubt many of them have planets, as 

 our sun has. No doubt there are living populations, 

 with ideas and institutions, on many of these planets. 

 All these are contents of our universe. There are 

 also incompletely developed stars, dead stars, and 

 masses of loose material that may one day form stars. 

 That is our universe. 



I keep repeating the word *'our" because it is 



