the skulls of the natives of the Sandwich Islands; on the hatching of
the eggs in the mouths and branchial cavities of male fishes.
Xenarchus, on the Cicadae.
Xenophon, selection in mankind advocated by.
Xenorhynchus, sexual difference in the colour of the eyes in.
Xiphophorus Hellerii, peculiar anal fin of the male.
Xylocopa, difference of the sexes in.
Yarrel, W., on the habits of the Cyprinidae; on Raia clavata; on the
characters of the male salmon during the breeding season; on the
characters of the rays; on the gemmeous dragonet; on colours of salmon;
on the spawning of the salmon; on the incubation of the Lophobranchii;
on rivalry in song-birds; on the trachea of the swan; on the moulting
of the Anatidae; on the young of the waders.
Yellow fever, immunity of negroes and mulattoes from.
Youatt, Mr., on the development of the horns in cattle.
Yura-caras, their notions of beauty.
Zebra, rejection of an ass by a female; stripes of the.
Zebus, humps of.
Zigzags, prevalence of, as ornaments.
Zincke, Mr., on European emigration to America.
Zootoca vivipara, sexual difference in the colour of.
Zouteveen, Dr., polydactylism; proportion of sexes at Cape of Good
Hope; spiders attracted by music; on sounds produced by fish.
Zygaenidae, coloration of the.
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