86 THE PHYSIOLOGY OF THE COMMON CRAYFISH. 
alimentation in a well-fed Crayfish 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. 
