Darwin's work on.
-difficulty of experimenting with.
-dimorphism of.
-dimorphism lost by variation.
-entrance of pollen-tubes at chalaza.
-varying fertility of.
-fertilisation of.
-homomorphic unions and.
-ovules of.
-J. Scott's work on.
-stamens of.
-P. elatior.
-P. longiflora, non-dimorphism of.
-Treviranus on.
-P. mollis.
-P. scotica.
-P. sinensis.
-fertility of.
-legitimate and illegitimate unions.
-movement of cotyledons.

Principle of divergence.

"Principles of Biology," Spencer's.

"Principles of Geology," Lyell's.
-Darwin on.
-Wallace's review of.

Pringlea antiscorbutica (Kerguelen cabbage).

Priority, Falconer and Owen on.

Proboscidean group, extinction of.

Progress, in forms of life and organisation.

Progression, tendency in organisms towards.

Progressive development.

Pronuba, the Yucca moth, Riley on.

Proteaceae, former extension of.

Protean genera, list of N. American.

Protection, colour in butterflies and.
-thorns as.
-Wallace on.
-colour and.
-colour of birds and.
-colour of caterpillars and.
-colour of shells and.
-Darwin's views on Sexual Selection and.
-evolution of colour and.
-mimicry and.
-monkeys' manes as.
-Wallace on colour and.
-Wallace on wings of lepidoptera and.

Protective resemblance, Wallace on.

Proterogyny, in Plantago.

Prothero, G.W.

Protococcus.

Protozoa.

Providential arrangement.

Prunus laurocerasus, extra-floral nectaries visited by ants.

Psithyrus.

Psychology, Delboeuf on.
-Romanes' work on comparative.

Ptarmigan, protective colouring of.

Pterophorus periscelidactylus.

Publishing, over-readiness of most men in.

Pumilio argyrolepis, Darwin on seeds of.

Purbeck, Plagiaulax from the.

Purpose, Darwin on use of term.

Pyrola, fertilisation mechanism in.

Quagga, hybrid between horse and.

Quails, seed-dispersal by migratory.

"Quarterly Journal of Science," article on Darwin and his teaching in.
-review by Wallace of the Duke of Argyll's "Reign of Law."

"Quarterly Review," Mivart's article.
-Bishop Wilberforce's review of "Origin" in.
-article on zebras, horses, and hybrids.

Quartz, segregation in foliated rocks.

Quatrefages, Jean Louis Armand de, de Breau (1810-92): was a scion of an
ancient family originally settled at Breau, in the Cevennes. His work was
largely anthropological, and in his writings and lectures he a