GROWTH. 115 



the larger Mammalia and Beptilia, were creatures incapable 

 of flight — creatures which did not expend this excess of 

 force in locomotion. Further evidence that there is 



an antagonism between the increase of bulk and the quantity 

 of motion evolved by an organism, is supplied by the ge- 

 neral experience, that human beings and domestic animals, 

 when overworked while growing, are prevented from attain- 

 ing the ordinary dimensions. 



One other general truth concerning degrees of growth, 

 must be set down. It is a rule, having exceptions of no 

 great importance, that large organisms commence their 

 separate existences as masses of organic matter more or less 

 considerable in size, and commonly with organizations more or 

 less advanced; and that throughout each organic sub-kingdom, 

 there is a certain general, though irregular, relation between 

 the initial and the final bulks. Yegetals exhibit this 



relation much less clearly and constantly than animals. Yet 

 though, among the plants that begin life as minute spores, 

 there are some which, under their special conditions, grow to 

 considerable sizes, the immense majority of them remain 

 small. While, conversely, the great Endogens and Exogens, 

 when thrown off from their parents, have already the formed 

 organs of young plants, to which are attached large stores of 

 highly nutritive matter. That is to sa} r , where the young 

 plant consists merely of a centre of development, the ultimate 

 growth is commonly insignificant ; but where the growth 

 is to become great, there exists to start with, a well-developed 

 embryo and a stock of assimilable matter. Through- 



out the animal kingdom, this relation is tolerably regular. 

 Save among classes that escape the ordinary requirements of 

 animal life, small germs or eggs do not give rise to bulky 

 creatures. Where great bulk is to be reached, the young 

 proceeds from an egg of considerable bulk, or is born of con- 

 siderable bulk ready-organized and partially active. In the 

 class fishes, for instance, a certain average proportion obtains 

 between the sizes of the ova and the sizes of the adult indi- 



