CONTENTS OF VOL. I. XIX 



— Investigation needed — The dog and the pigeon — The most constant characters 

 in species are also the most constant in classes — Bones of pterodactyle — The 

 lowest organisms are most variable— Parts repeated many times are variable — 

 Eeason of these two laws — Summary — Third class of changes — Crystals vary 

 with the medium from which they are deposited — Similar variations in fungi 

 — Functionally produced modifications in fungi — Origin of Entozoa — Their 

 metagenesis. 

 Note : Individual iUj : — Individuality, difficult to deiine among the lower organ- 

 isms — Morphological units of different orders Pp. 187 — 204 



CHAPTER XVII. 



THE PROBLEM OF THE ORIGIN OF SPECIES. 



Have all species been separately created, or derived from a few original germs ? — 

 I believe the latter. Where I dissent from Darwin — I believe in a guiding 

 Intelligence — Development theory, not contrary to experience — Changes in 

 language — Geological changes — No intrinsic improbability — Analogy of indi- 

 vidual development — Subject not yet familiar — Separation of species by mutual 

 sterility, not absolute — Eeason of mutual sterility unknown — Suggestion on 

 the subject — Transitional forms, often still in existence, but mostly lost — 

 Imperfection of the geological record — Destruction of fossils — Denudation — 

 Iiletamorphism — Discovery of intermediate forms — Reptilian birds — Variability 

 of histological characters — Species are permanent varieties — Varieties are most 

 numerous where species are so — Aberrant genera are poor in species — Charac- 

 ters variable as between species are so within the species— "Wings of beetles — 

 Reversion in varieties, and in species — Species of Equus — Laws of variation, 

 and of reversion — Extension of the above-stated law of variation — Wings of 

 insects — Branchife of Mollusca— Development of Echinodennata — Extension 

 of the above-stated law of reversion — <.^ircular and bilateral flowers— Peloria — 

 Non-sexual generation in worms, Cnistacea, and insects. 



jg'oTE : — Is there a limit to variation ? — I maintain the negative, in opposition 



to usual belief — Argument of North British reviewer for the affirmative — Limit 



of smallness in dogs has been attained — Variation held in check by reversion 



— Tendency to revert may die out with lapse of time, and limit to variation 



' may recede — Reason of the possibility of this Pp. 205— 218 



CHAPTER XVIII. 



DISTRIBUTION. 



Cuvier's doctrine of organic adaptation — Functional and structural adaptations — 

 The form of each part is determined by the rest, and all by the animal's life — 

 This is true : but will it explain all the facts ? — We must admit a further prin- 

 ciple — Bearings of Cuvier's doctrine on morphology and on distribution — 

 External circumstances do not determine distribution — Mountain species — Dis- 



