236 THE INDUCTIONS OF BIOLOGY, 



and limited to that quantity of prey which, chance brings 

 within its grasp ; buds out young polypes which, either as a 

 colony or as dispersed individuals, spread their tentacles 

 through a larger space of water than the parent alone can ; 

 and by producing them, the parent better insures the continu- 

 ance of its species, than it would do if it went on slowly grow- 

 ing until its nutrition was nearly balanced by its waste, and 

 then multiplied by gamogenesis. Similarly with the Aphis. 

 Living on sap sucked through its proboscis from tender shoots 

 and leaves, and able thus to take in but a very small quan- 

 tity in a given time, this creature's race is more likely to 

 be preserved by a rapid asexual propagation of small indi- 

 viduals, which disperse therdselves over a wide but nowhere 

 rich area of nutrition, than it would be did the individual 

 growth continue so as to produce large individuals multiply- 

 ing sexually. While at the same time we see, that when 

 autumnal cold and diminishing supply of sap, put a check to 

 growth, the recurrence of gamogenesis, and production of 

 fertilized ova that remain dormant through the winter, is 

 more favourable to the preservation of the race, than would be 

 a further continuance of agamogenesis. On the 



other hand, it is obvious that among the higher animals, 

 living on food which, though dispersed, is more or less 

 aggregated into large masses, this alternation of gamic and 

 agamic reproduction ceases to be useful. The development 

 of the germ-product into a single organism of considerable 

 bulk, is in many cases a condition without which these large 

 masses of nutriment could not be appropriated ; and here the 

 formation of many individuals instead of one, would be fatal. 

 But we still see the beneficial results of the general law — the 

 postponement of gamogenesis until the rate of growth begins 

 to decline. For so long as the rate of growth continues 

 rapid, it is a proof that the organism gets food with great 

 facility — that expenditure is not such as seriously to check 

 accumulation ; and that the size reached is as yet not disad- 

 vantageous — or rather, indeed, that it is advantageous. But 



