Now understands importance of swim-bladder in selachians. Always imagined animal like Lepidosiren was parent form of vertebrates.

Has been nearly a month in London, collecting facts on sexual selection from breeders and at Zoological Gardens.

Astonished at hybrid of rabbit and hare. Is it certain that work was done with hare?

Has received English edition of Variation. First volume of German edition came three months ago. Comments on book.

Will send copy of recent lectures on human evolution [Entstehung des Menschengeschlechts (1868)]. Gegenbaur much interested in the subject.

Considers Selachius the ancestral form of the fish and hence of all higher vertebrates. Believes their swim-bladder became lung of amphibians.

Mentions cases of hybrid crosses between rabbits and hares producing fertile offspring.