292 SIGNIFICANCE OF SEXUAL REPRODUCTION [V. 



such a power can be weakened and finally entirely lost while 

 one of its components is accumulated? 



I believe that, instead of accepting such daring assumptions, 

 it is better to be satisfied with the simple conception of living 

 matter possessing as attributes the powers of unlimited assi- 

 milation and capacity for reproduction. With such a theory 

 the mere form of reproduction, whether sexual or asexual, will 

 have no influence upon the duration of the capacity : for force 

 and matter undergo simultaneous increase, and are inseparably 

 connected in this as in all other instances. This theory does 

 not, however, exclude the possible occurrence of circumstances 

 under which such an association is no longer necessary. 



I could only consent to adopt the hypothesis of rejuvenes- 

 cence, if it were rendered absolutely certain that reproduction 

 by division could never under any circumstances persist in- 

 definitely. But this cannot be proved with any greater 

 certainty than the converse proposition, and hence, as far 

 as direct proof is concerned, the facts are equally uncertain 

 on both sides. The hypothesis of rejuvenescence is, however, 

 opposed by the fact of parthenogenesis ; for if fertilization 

 possesses in any way the meaning of rejuvenescence, and 

 depends upon the union of two different forms of force and 

 of matter, which thus produce the power of reproduction, it 

 follows that we cannot understand how it happens that the 

 same power of reproduction may be sometimes produced from 

 one form of matter, alone and unaided. Logically speaking, 

 parthenogenesis should be as impossible as that either nitric 

 acid or glycerine should separately produce the effect of nitro- 

 glycerine. The supposition has indeed been made that in 

 the case of parthenogenesis, one fertilization is sufficient for 

 a whole series of generations, but this supposition is not 

 only incapable of proof, but it is contradicted by the fact that 

 certain eggs which may develope parthenogenetically are also 

 capable of fertilization. If, in this case, the power of repro- 

 duction were sufficient for development, how is it that the 

 egg is also capable of fertilization ; and if the power were 

 insufficient, how is it that the ^g^^ can develope partheno- 

 genetically ? And yet one and the same ^^% (in the bee) can 

 develope into a new individual, with or without fertilization. 

 We cannot escape this dilemma by making the further as- 



