Chap, ii.] OJF GENERATION IN THE TWO KINGDOMS. 811 



reduces itself always and everywhere to the conjugation of two 

 cells, and the absorption of one by the other. The names 

 change, but the phenomenon is essentially the same, whether 

 we contemplate the oosphere and the antherozoids of the algie, the 

 embryonary sac and the pollen of the phanerogams, the ovulum 

 and the spermatozoaries of the animals. The oosphere, the em- 

 bryonary sac, the bvulum ai-e simple varieties of the female 

 element, as the antherozoids, the poUioical cells, the speiina- 

 tozoaries are varieties of the male element. 



Between the organisms in which reproduction is efiected by 

 simple bipartition, and those in which it is only possible after 

 the fusion of a female cell and a male cell, that is to say, after 

 a fecundation we can place the cases of parthenogenesis, the most 

 celebrated example of which is that of the aphides. Here the 

 intervention of the male cell is only necessaiy after long 

 intervals. If it has once taken place it suffices for the forma- 

 tion of a series of ovula, to which it is no longer indispensable, 

 and the female can afterwards engender, without the co-operation 

 of the male, a whole line of young. But little by little the 

 field of evolution is abridged for each new ovulum : the pro- 

 ducts are more and more imperfect, more and more incomplete : 

 finally the evolutive force of the ovula is extinguished, is 

 exhausted, and their revivification by a new sexual, impregna- 

 tion becomes the very condition itself of generation.^ 



In most plants, in a great number of inferior bisexuate 

 animals, the male and female apparatus are united in the same 

 individual. Then autofecundation is often possible : sometimes 

 also it is impossible. But even in the first case the diversity of 

 origin of the male and female sexual elements is a condition 

 most frequently favourable, sometimes iadispensable to fecunda- 

 tion. The observations and experiments of Sprengel and Darwin 

 have demonstrated that nearly all hermaphrodite plants need, to 

 fructify, a cross fecimdation. To use the expression of Darwin, 



^ See CI. Bernard, Des PMnomines de- la Vie communs aux Anmumx ei aux 

 Vegitcmx {Jievue Scieiitifique, 1874). 



