180 THE ANATOMY OF SCIENCE 



low temperatures, and when it is brought into 

 contact with block tin it spreads as the crystals 

 just now spread in the beaker. 



A salt often crystallizes in a number of dif- 

 ferent ways, but these ways seem to be fixed 

 through the ages, and the crystals that we find 

 in geological deposits are not distinguishable 

 from those which we now grow in the labora- 

 tory. But the horse, while apparently much the 

 same from one generation to another, is very 

 different from his tiny five-toed ancestor, which 

 in its turn probably bore little outward resem- 

 blance to the reptihan ancestor that was living 

 at the time of the salt deposits of which I have 

 just spoken. I must present later my apologies 

 for violating one of the most sacred taboos of 

 biological science when I state that the essential 

 difference between the reproduction of the crys- 

 tal and the reproduction of an organism is that 

 the latter is reproduced with the transmission of 

 acquired characteristics. Inanimate things we 

 describe as obeying laws which are fixed for all 

 time, but the living organism is an opportunist, 

 making new laws from time to time in its con- 

 stant evolution. 



It is easy enough to make such an abstract 

 classification, but do we know that any sub- 



