158 THE INDUCTIONS OF BIOLOGY. 



ones, gradually lose that surplus of assimilative power which 

 they had, and eventually cannot assimilate more than is re- 

 quired to balance waste. But how come these animals while 

 young and small to have surplus assimilative powers? Have 

 all animals equal surpluses of assimilative powers? And 

 if not, how far do differences between the surpluses de- 

 termine differences between the limits of growth ? We 

 shall find, in the answers to these questions, the interpretation 

 of many marked contrasts in growth that are not due to any 

 of the causes above assigned. For example, an ox immensely 

 exceeds a sheep in mass. Yet the two live from generation 

 to generation in the same fields, eat the same grass, obtain 

 these aliments with the same small expenditure of energ}^ 

 and differ scarcely at all in their degrees of organization. 

 Whence arises, then, their striking unlikeness of bulk? 



We noted when studying the phenomena of growth in- 

 ductively, that organisms of the larger and higher types com- 

 mence their separate existences as masses of organic matter 

 having tolerable magnitudes. Speaking generally, we saw 

 that throughout each organic sub-kingdom the acquirement 

 of great bulk occurs only where the incipient bulk and or- 

 ganization are considerable; and that they are the more con- 

 siderable in proportion to the complexity of the life which 

 the organism is to lead. 



The deductive interpretation of this induction may best 

 be commenced by an analogy. A street orange-vendor 

 makes but a trifling profit on each transaction; and unless 

 more than ordinarily fortunate, he is unable to realize 

 during the day a larger amount than will meet his wants; 

 leaving him to start on the morrow in the same condition 

 as before. The trade of the huxter in ounces of tea and 

 half-pounds of sugar, is one similarly entailing much labour 

 for small returns. Beginning with a capital of a few 

 pounds, he cannot have a shop large enough, or goods 

 sufficiently abundant and various, to permit an extensive 

 business. He must be content with the half -pence and pence 



