LIFE IN THE PAST 159 
interesting next to consider what the biologist sur- 
mises as to the origin of the life upon the earth. 
Here again two explanations hold. The one, and dis- 
tinctly the older of the two, says that at some time 
in the far distant past, under conditions which are 
rarely if ever duplicated, out of the lifeless material 
of the globe were produced simple and low forms of 
life. These could not properly be called either animal 
or plant, but partook somewhat of the nature of both. 
Of this there is at present no evidence whatever. The 
only reason we have for suggesting it is that, if we 
understand the past conditions on the earth, there was 
a time when life was impossible. Now we find life. 
Hence it must have arisen. This of itself, of course, 
furnishes no proof, but leads us to try to imagine how 
the transition might have come about. Every scien- 
tist who believes in this form of origin holds that if 
the exact conditions are repeated the result will occur 
once more. He may believe that no such repetition 
is possible, but he is confident that, if it could be, life 
would arise again from lifeless matter. 
This process of life arising from matter that is not 
alive is known as Spontaneous Generation. Two hun- 
dred years ago it was supposed to occur frequently. 
It was common belief that the beautiful pickerel weed 
which borders our Northern lakes, after freezing, went 
into a sort of protoplasmic slime out of which pick- 
