298 THE EVOLUTION OF SEX. 



parallelism and coincidence of psychical and material considera- 

 tions, upon which moralist and economist have been too much 

 wont respectively to specialise. 



§ 6. Rate of Reproduction ''^ Nil" — Sterility. — When we view 

 reproduction in terms of discontinuous growth, — that is, as a 

 phenomenon of disintegration, — it is obvious that complete 

 integration of the matter acquired by the organism into its own 

 bulk, and for its own development, precludes reproduction, — 

 that is, involves sterility, — and similarly as regards the energies 

 of the organism. This is only a re-statement of Spencer's 

 generalisation above discussed ; for it is evident that, if genesis 

 vary inversely as individuation, it must be suppressed altogether 

 if individuation becomes complete. The actual phenomena, 

 however, by no means usually admit of explanation as such 

 realisations of the ideal of evolution, and hence the cause and 

 treatment of sterility mainly pass into the provinces of the 

 experimental naturalist and the physiological physician. From 

 the earliest times, indeed, physician and naturalist, priest and 

 legislator, alike devoted attention to the subject ; and it was 

 probably in this way, as a recent monographer remarks, that 

 research became directed to the larger problem of repro- 

 duction in general. The general biological questions — 

 e.g.^ the relations between sterility within the limits of 

 a species to changes in the environment, or that of sterility 

 among hybrids — are extensively discussed in the copious 

 literature which centres around Darwin's Variatio?i of A?ii7tials 

 a?id Plants under Domestication ; while with regard to the 

 human species, an extensive medical literature of course exists, 

 to which any encyclopedia of medicine, or conveniently the 

 recent careful monograph of P. Miiller {Die Ufifruchtbarkeit 

 der Ehe^ Stuttgart, 1885), will furnish bibliographical details. 



