230 THE INDUCTIONS OF BIOLOGY. 



in each ovarium, amounts, under favourable circumstances, 

 to as many as eight or nine ; while of the gamic eggs, only 

 one at a time is produced in each ovarium, and occasionally 

 one of the ovaria produces none : whence it follows, that as 

 the gamic egg is not more than twice the bulk of the agamic 

 egg, the quantity of matter contained in an agamic brood, is 

 four times, and occasionally even eight time3, as great as 

 that contained in a gamic brood. Thus the quantity of 

 nutriment expended in gamogenesis during a given period 

 (making allowance for that which goes to the formation of 

 the ephippium), is far less than that expended in agamogenesis 

 during a like period. Seeing, then, this constant preparation 

 for either gamic or agamic genesis, in a creature liable to 

 such irregular variations of nutrition ; and seeing that the 

 agamogenesis implies by its amount, a large excess of nutri- 

 tion, while the gamogenesis implies by its amount, a small 

 excess of nutrition ; we can scarcely doubt that the one or 

 the other mode of multiplication occurs, according as the 

 external conditions are or are not favourable to nutrition. 



Passing now to animals which multiply by homogenesis — ■ 

 animals in which the whole product of a fertilized germ ag- 

 gregates round a single centre or axis, instead of round many 

 centres or axes ; we see, as before, that so long as the con- 

 ditions allow rapid increase in the mass of this germ-product, 

 the formation of new individuals by gamogenesis does not 

 take place. Speaking generally, we find that only when 

 growth is declining in relative rapidity, do perfect sperm- 

 cells and germ-cells begin to appear; and that the fullest 

 activnty of the reproductive function, arises as growth ceases 

 — speaking generally, we must say, because, though this 

 relation is tolerably definite in the highest orders of animals 

 which multiply by gamogenesis, it is less definite in the lower 

 orders. This admission does not militate against the hypo- 

 thesis, as it seems to do ; for the indefiniteness of the relation 

 occurs where the limit of growth is comparatively indefinite. 

 We saw (§ 46) that among active, hot-blooded creatures, 



