158 THE EVOLUTION OF SEX. 



concentrated essence of the whole body. But it was only after 

 the spermatozoa were themselves detected that their importance 

 became unduly exaggerated, in the minds of those who seem 

 almost to have been nicknamed "animalculists." It seems 

 probable enough that Leeuwenhoek himself (1677) saw the 

 spermatozoon entering the ovum, — he at least said that he did, 

 — but that did not prevent him from ascribing to the male 

 elements all the credit of development. This became, as we 

 have seen, a favourite hypothesis, and imagination supplied 

 more than modern magnifiers to those observers who detected 

 in the spermatozoon the members and lineaments of the 

 future organism. After this the discovery that the sperm 

 supplies half the nucleus of the fertihsed ovum, and half the 

 nuclei of the two first daughter-cells, seems almost a little thing. 

 The polemic of modern science has this advantage at least, that 

 when two competent authorities on the same subject assert the 

 same thing, we may generally believe them. 



(c) The third opinion, that both elements are of essential 

 and inseparable import, is obviously alone consistent with the 

 facts. This view also has had its gradual development, only 

 one phase of which need be noticed. Even after the nature oi 

 the spermatozoa as male-cells was recognised, that is to say, even 

 within the last fifty years, an old conception of the male in- 

 fluence lingered persistently. This namely, that contact was 

 not essential, but that a "sort of contagion,'"' a "breath or 

 miasma," "a plastical vertue," "without touching at all, unless 

 through the sides of many mediums," was sufficient to effect 

 what we call fertilisation. The above expressions are used by 

 Harvey, who further says, " this is agreed upon by universal 

 consent, that all animals whatever, which arise from male and 

 female, are generated by the coition of both sexes, and so 

 begotten as it were per confagium aliquod'' De Graaf attempted 

 in vain to give more precision to this " contagion " in his theory 

 of an ^^ aura seminalis,'' or seminal breath which passed from 

 the male fluid to the ovum. But the conception of an "aura " 

 was only a verbal cloak for that absence of definite knowledge 

 which the slow progress of observation still necessitated. The 

 theory was partly strengthened by a number of erroneous obser- 

 vations, which seemed to show that successful fertilisation could 

 occur when the genital passages of the female were apparently 

 blocked by malformation or disease. Spallanzani gave a death- 

 blow to the theory of an "' aura, "^ by showing experimentally 



