I^O THE EVOLUTION OF MAN. 



higher plants and animals this constitutes the first act in 

 which the evolution of the new individual begins. But 

 it must be noted here that this important process is by no 

 means as universally distributed throughout the animal and 

 vegetable world as is commonly supposed. On the contrary, 

 there are very many low organisms which always multiply 

 asexually, e.g. the Amrebse, Gregarinse, Flagellata, Forami- 

 niferse, Radiolaria. Myxomycetse, etc. In these cases 

 there is no form of impregnation : the multiplication of 

 individuals, and the preservation of the species depend here 

 simply on asexual generation, under the forms of fission, 

 propagation by buds or by germ-cells. On the other hand, 

 in the case of all higher plant and animal organisms, sexual 

 propagation is the general law, and asexual generation 

 never or but seldom occurs. Among Vertebrates in par- 

 ticular "virginal generation" (Parthenogenesis} never 

 occurs. This we must explicitly affirm in the face of the 

 celebrated dogma of the "immaculate conception." "Im- 

 maculate conception" has never been observed either in 

 Man, or in any other Vertebrate. 4 ? 



Sexual propagation in the various classes of animals 

 and plants exhibits an especially large number of interest- 

 ing correlations, especially those relating to fertilization 

 and the transmission of the male sperm to the female egg. 

 These correlations are of the utmost significance not only in 

 regard to propagation, but also in the production of organic 

 bodily forms, and especially of sexual differences. Very 

 remarkable instances of interaction take place between 

 plants and animals. The recent admirable researches of 

 Darwin and Hermann Muller on the fertilization of flowera 

 by insect agency, are especially interesting from this point 



