184 THE THEORY OF NATURAL SELECTION. 



may be the offspring are always the most numerous. 

 Seeds of all kinds are immeasurably greater in numbers 

 than the plants which produce them ; in some cases 

 hundreds of thousands being furnished by a single plant. 

 In animals also this prodigality of reproduction obtains in 

 the quantities of ova and of young which are brought into 

 existence. 



An instance of this prolific reproductive facult\' is 

 found in the common ghost moth [Hepialiis /iiiiiniit), 

 which deposits upwards of 800 eggs. If it is assumed 

 that half these ova produce female moths : that these in 

 turn each lay the same number of eggs and that the 

 generations be continued for five years without check or 

 interruption, the fifth generation from a single pair of these 

 insects would number more than eighty millions of millions 

 of millions of moths. It has been shewn that if the average 

 offspring of one oyster could by any possibility breed and 

 accumulate without hindrance for only five generations 

 their numbers would be represented by the figure 6 with ^^ 

 noughts behind it, and that the mass of their shells would 

 be equal to eight times that of the earth. 



Notwithstanding, however, the rapid increase of all 

 forms of life the total number of living things is practically 

 stationary, and in a case where there may be a temporary 

 or permanent addition to the numbers of an animal or of 

 a plant, the increase is made at the expense, and sometimes 

 at the complete sacrifice, of some other animal or vegetable, 

 or possibly of both, which would be deprived oi the share 

 of the room and the food necessary to existence. 



There arises, therefore, amongst all living things, a 

 constant struggle, for life first and for supremacy afterwards, 

 and this warfare is continually in progre.'-s throughout the 

 biological world. Every plant and every animal appears to 

 be doing its utmost to increase its numbers, the struggle 



