318 THE CELL 



fertilisation consists in "mixing slightly different physiological 

 units of slightly different individuals." * 



Herbert Spencer (IX. 26) availed himself of these experiments 

 of Darwin's, in order to build up a molecular theory of the nature 

 of fertilisation, which deserves notice as a preliminary attempt. 



Spencer, to a certain extent, states as an axiom, that the need 

 of fertilisation of the sexual cell " recurs only when the organic 

 units (micellae) are approximating to equilibrium only when 

 their mutual restraints prevent them from readily changing their 

 arrangements in obedience to incident forces." 2 



If this hypothesis, which appears to me to be at present but a 

 possibility, could be proved, we could certainly accept without 

 further consideration Spencer's explanation: " Gamogenesis 

 (sexual reproduction) has for its main end, the initiation of a new 

 development by the overthrow of that approximate equilibrium 

 arrived at amongst the molecules of the parent organism." 3 For 

 " by uniting a group of units from the one organism with a group 

 of slightly different units from the other the tendency towards 

 equilibrium will be diminished, and the mixed units will be ren- 

 dered more modifiable in their arrangements by the forces acting 

 on them ; they will be so far freed as to become again capable of 

 that redistribution which constitutes evolution." 4 



In this sense, fertilisation may be considered to be a process of 

 rejuvenation, to employ the expression used by Butschli (VII. 6), 

 Maupas (VII. 30), and others. 



Spencer's statement at present lacks an exact and scientific 

 foundation, but it seems to deserve notice as a preliminary at- 

 tempt to solve this extremely difficult question. 



An important conclusion may be deduced from the above- 

 mentioned principle, that the process of fertilisation consists in 

 the " mixing of slightly different physiological units of slightly 

 different individuals." If sexual reproduction is a mingling of the 

 properties of two cells, it must result in the development of inter- 

 mediate forms. 



Thus reproduction, so to speak, strikes a balance between 



1 The first of these quotations is taken from Darwin's Origin of Species, 

 p. 432, and the second and third from Darwin's Cross- and Self -fertilisation of 

 Plants, pp. 462, 463. 



2 Principles of Biology, by Herbert Spencer, vol. i. p. 275. 



3 Ibid., p. 284. 



4 Ibid., p. 277. 



