Contents 
PAGE 
importance of Mendelism has been exaggerated—Dominance 
sometimes imperfect—Behaviour of the nucleus of the sexual cell 
~—Chromosomes—Experiments of Delage and Loeb—Those of 
Cuénot on mice and Castle on guinea pigs—Suggested modifica- 
tion of the generally-accepted Mendelian formulze — Unit 
characters—Biological isomerism—Biological molecules—Inter- 
pretation of the phenomena of variation and heredity on the 
conception of biological molecules—Correlation—Summary of 
the conception of biological molecules. 
CHAPTER VI 
THE COLOURATION OF ORGANISMS . : . 170 
The theory of protective colouration has been carried to absurd 
lengths—It will not bear close scrutiny—Cryptic colouring 
—Sematic colours — Pseudo-sematic colours — Batesian and 
Miillerian mimicry — Conditions necessary for mimicry — 
Examples—Recognition markings—The theory of obliterative 
colouration—Criticism of the theory—Objections to the theory of 
cryptic colouring—Whiteness of the Arctic fauna is exaggerated 
—lIlilustrative tables—Pelagic organisms—Objectors to the Neo- 
Darwinian theories of colouration are to be found among field 
naturalists—G. A. B. Dewar, Gadow, Robinson, F, C. Selous 
quoted—Colours of birds’ eggs—Warning colouration— Objec- 
tions to the theory—Eisig’s theory—So-called intimidating 
attitudes of animals—Mimicry—The case for the theory—The 
case against the theory—“ False mimicry ’—Theory of recogni- 
tion colours—The theory refuted—Colours of flowers and fruits 
—Neo-Darwinian explanations—Objections—Kay Robinson’s 
theory—Conclusion that Neo-Darwinian theories are untenable 
—Some suggestions regarding the colouration of animals— 
Through the diversity of colouring of organisms something like 
order runs—The connection between biological molecules and 
colour—Tylor on colour patterns in animals—Bonhote's theory 
of poecilomeres—Summary of conclusions arrived at. 
CHAPTER VII 
SExUAL DIMORPHISM . : . . . 297 
Meaning of the term—Fatal to Wallaceism—Sexual Selection—The 
law of battle—Female preference—Mutual Selection — Finn’s 
experiments — Objections to the theory of Sexual Selection— 
Wallace’s explanation of sexual dimorphism stated and shown 
to be unsatisfactory—The explanation of Thomson and Geddes 
shown to be inadequate—Stolzmann’s theory stated and criticised 
XV 
