RUDIMENTARY REPRODUCTIVE SYSTEM. 391 



the opposed differentiation of the two sexes is the condition. 

 In my Generelle Morphologie (vol. ii. pp. 32-71), and in 

 my " Natural History of Creation " (voL i p. 183), I 

 have fully discussed the connection of these various forma 

 of reproduction. 



None of the earliest ancestors of Man and of the higher 

 animals were capable of the higher function of sexual 

 reproduction, but multiplied only in an asexual manner, by 

 division or gemmation, by the formation of germ-buds, or of 

 germ-cells, as is still the case with most Primaeval Animals 

 or Protozoa. It was not until a later period in the organic 

 history of the earth, that sexual difference of the two 

 sexes could arise ; and this took place at first in the 

 simplest manner by the severance of two cells which 

 amalgamated from the community of the many-celled 

 organism. We may say that, hi this case, growth, which is 

 the condition necessary to reproduction, was attained by 

 the union of two full-grown cells into a single cell which 

 then exceeded its proper size ("copulation" or conjuga- 

 tion"). At first, the two united cells may have been 

 entirely alike. Soon, however, by natural selection, a con- 

 trast must have arisen between them. For it must have 

 been very advantageous to the newly-created individual in 

 the struggle for existence, to have inherited various quali- 

 ties from the two parent-cells. The complete development 

 of this progressive contrast between the two producing 

 cells, led to sexual differentiation. One cell became a 

 female egg-cell, the other, a male seed or sperm celL 



The simplest form of sexual reproduction among existing 

 animals, is exhibited in Gastrseads and the lower Sponges, 

 especially the Chalk Sponges, and, also, in the simplest 



