86 THE PHYSIOLOGY OF THE COMMON CRAYFISH. 



alimentation in a well-fed Craj'fisli were extended over a 

 longer time, say a year or two, we should find that the 

 products given out were no longer equal to the materials 

 taken in, and the balance would be found in the increase 

 of the animal's weight. If we inquired how the balance 

 was distributed, we should find it partly in store, chiefly 

 in the shape of fat ; while, in part, it had been spent in 

 increasing the plant and in enlarging the factory. That 

 is to say, it would have supplied the material for the 

 animal's growth. And this is one of the most remark- 

 able respects in which the living factory differs from 

 those which we construct. It not only enlarges itself, 

 but, as we have seen, it is capable of executing its own 

 repairs to a very considerable extent. 



