SUMMARY OF CHAPTERS IX 



PAGES 



between the utility of a variation and its production — ^The 

 luminous apparatus of deep-sea fishes. 

 3. Co-operation between natural selection and germinal selection 

 — Germinal selection effectuates variations of morphological 

 value, natural selection effectuates variations of biological value 

 — ^Pore-wing of PhyUodes ornata — Tendency of the determinants 

 to vary — Nevertheless, many species remain constant during long 

 periods — The reason of this constancy is to be sought for in the 

 inhibitory action of natural selection, which regulates the force of 

 the variations in the germ-plasm — Only variations of morpho- 

 logical value are controllable by germinal selection — Plus-varia- 

 tions in one group of determinants entail minus-variations in other 

 groups — Mutations — ^No antithesis between constancy and 

 adaptability — Specific psychical talents — The musical faculty — 

 Correlation of psychical faculties in genius — All the changes in 

 the germ-plasm are quantitative in their nature - 41-64 



CHAPTER IV 

 The Lamaeckian Hypothesis of the iNHEBiTAifOE or Acquibed 



Chabacters 



1. Contradiction between the theory of Weismann and that of 



Lamarck — Dntenability of the Lamarckian hypothesis — The 

 results of mutilation — Experiments of Weismann — Inborn 

 mutilations different to acquired mutilations — Adverse evidence 

 of cattle-breeders — Acquired and transmissible diseases- — Disease 

 can affect the germ-plasm as much as the soma — Syphihs 

 and alcoholism • — Tuberculosis is transmitted indirectly, not 

 directly — Cancer not hereditary — The alleged transmission of 

 epilepsy — Experiments of Brown-Sequard — Unsatisfactory 

 character of these experiments — ^A general pathological condition 

 is transmitted, not the disease itself. 



2. The case of instinct — Instinct as "inherited habit" — Refu- 



tation of this conception of instinct — Instincts which manifest 

 themselves but once in a hfetime — Natural selection suffices 

 to explain the phenomenon of instinct — An act of vohtion can 

 become instinctive — Instinct can occasionally be the result of 

 tradition— Modification of the passive parts of the organism — 

 Regression of the wings and ovaries of worker-ants — The bio- 

 genetic law — Harmony between the biogenetic law and the 

 determinant theory — Co-adaptation— The horns of the Irish stag 

 — Useful variations not only possible, but necessary — Formation 

 of the membranes of insects .... . 65-84 



