Il8 THE EVOLUTION OF SEX. 



Mi not, in his " theory of gehoblasts," or sexual elements, 

 ventures little further than regarding male and female as 

 derivatives of primitive hermaphroditism in two opposite 

 directions. " As evolution continued, hermaphroditism was 

 replaced by a new differentiation, in consequence of which the 

 individuals of a species w-ere — some capable of producing ova 

 only, others of producing spermatozoa only. Individuals of 

 the former kind we call females, of the latter males, and they 

 are said to have sex." " At present all we can say is, we do 

 not know w^hy or how sexual individuals are produced." In 

 regard to the sex elements, we have already noticed his opinion 

 that they are at first " hermaphroditic or asexual," and that 

 both differentiate by the extrusion or separation of the con- 

 tradictory elements, the ovum getting rid of male polar globules, 

 the sperms leaving behind a female mother-cell-remnant. 



Brooks has emphasised rather a different aspect of the 

 question. "A division of physiological labour has arisen 

 during the evolution of life, the functions of the reproductive 

 elements have become specialised in different directions." 

 " The male cell became adapted for storing up gemmules, and, 

 at the same time, gradually lost its unnecessary and useless 

 power to transmit hereditary characteristics." "The males are, 

 as a rule, more variable than the females ; the male leads, and 

 the female follows, in the evolution of new races." Brooks 

 does not exactly attack the problem of the nature and origin of 

 sex, but his emphasis on the greater variability of males is of 

 much importance. 



These three positions must be taken as representative ; 

 others, which appeal to superiorities, polarities, and like mys- 

 teries, can hardly claim scientific standing, and have been 

 already sufficiently referred to at p. 33. To those which in- 

 terpret the sexes in terms of the advantages of sexual repro- 

 duction, and to those which deal almost exclusively with the 

 problem of fertilisation, w^e shall afterwards return. The truth 

 in fact is, that it is difficult to find any answer at once serious 

 and direct to the question of the fundamental difference between 

 male and female. 



5^2. Natiwe of Sex as seen iti the Sex-Elements — The Cell 

 Cycle. — As ova and sperms are the characteristic products of 

 female and male organisms, it is reasonable that an interpretation 

 of sex should start at this level. Here, assuredly, the difference 

 between male and female has its fundamental and most con- 



