xiv] STABILITY OF SPECIES 



For heredity has gone on increasing with the succession of geological 

 epochs, whilst on the other hand the force of plasmation has gradu- 

 ally grown weaker, and ceased entirely at the present day. 



Even those who decline to attribute importance to the force of 

 heredity because it cannot be experimentally demonstrated, or, as 

 some express it, because it is merely evoked to interpret phenomena 

 otherwise unexplainable, are compelled to admit that between the 

 reproductive phenomena of organisms in the primordial epoch of 

 the formation of species and those of to-day a difference must exist. 

 It is not within the bounds of credibility that all the reproductive 

 phenomena can have become manifest in the very same mode in the 

 primordial generations as after the lapse of thousands and thousands 

 of generations. In other words, it seems to me a bold thing to assert 

 that no change can have taken place in the effects of fecundation 

 since the first times when the parts forming the nuclei of organisms 

 of opposite sex met, united, and subsequently parted, to give origin 

 to the embryo of a new creature, and now, when the process of 

 fecundation and development has been reproduced for an indefinite 

 period and through an incalculable number of generations. It 

 appears to me that the stability obtained in the phenomena of re- 

 production, the primary cause of the stability of species, is a conse- 

 quence of the number of times these phenomena have repeated 

 themselves ; and also that the stability of the morphological char- 

 acters of individuals must be proportional in any given species to 

 the number of the generations of each, and to the length of time 

 since their specific entity was defined. It cannot be doubted that 

 in the nucleus of the reproductive cell are comprised all the here- 

 ditary and physical characteristics of the organisms to which that 

 cell belonged. Now, as it is inferred that every part and every organ 

 of any given living creature must have contributed to the formation 

 of its reproductive cells, into which infinitely minute particles repre- 

 senting each part and each organ must have been carried, it is pre- 

 sumable that in the far remote epochs of specific plasmation, when 

 organisms were assuming the shapes they have since retained, that the 

 transference into the cell nuclei of the infinitely minute particles of 

 protoplasm or micellae representing the various organs and parts of 

 the living being was partial and incomplete, so that, all the parts 

 of the parental organism not being fully represented, extensive 

 variation became possible ; but as generations succeeded to genera- 

 tions the transference of the protoplasmic micellae representing the 

 various parts of the parent into the tissue of the reproductive nuclei 

 became more general and complete, and the tendency to variation 

 naturally diminished gradually. At the present time, after an 

 infinite number of generations, the aforesaid transmission must have 

 become so complete that the field is closed to variation, and living 

 organisms are obliged to reproduce themselves with constant and 



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