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The fish, having remained in this distended state for a short time, generally expelled the air and water with considerable force from the branchial apertures and mouth. It could emit, at will, a certain portion of the water, and it appears, therefore probable that this fluid is taken in partly for the sake of regulating its specific gravity. This Diodon possessed several means of defence.

It can thus easily come and go and retire into its cave, where it finds security and a humidity favourable for branchial respiration. From time to time it cleans out the dirt and rubbish which accumulate in the hole. It makes a little pile of all the refuse which it finds, and, seizing it between its claws and abdomen, carries it outside.

Wyman, Prof., on the prolongation of the coccyx in the human embryo; on the condition of the great toe in the human embryo; on the occurrence of the supra-condyloid foramen in the humerus of man; on variation in 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.

In the middle line of its ventral side we find the hypobranchial groove. The ejection-opening of this peribranchial cavity corresponds to the branchial pore of the Amphioxus. In the adult Ascidia the branchial gut and the heart on its ventral side are almost the only organs that recall the original affinity with the vertebrates.

Man's ancestors are skull-less Vertebrates, like the Amphioxus. The body is a series of metamera, as several of the primitive segments are developed. The head contains in the ventral half the branchial gut, the trunk the hepatic gut. The medullary tube is still simple. No skull, jaws, or limbs. The number of metamera increases.

Geographical distribution, as evidence of specific distinctions in man. Geometrae, brightly coloured beneath. Geophagus, frontal protuberance of, male; eggs hatched by the male, in the mouth or branchial cavity. Georgia, change of colour in Germans settled in. Geotrupes, stridulation of. Gerbe, M., on the nest-building of Crenilabus massa and C. Melops.

Thus the two ridges of the right and left sides form together a triangle with the apex turned forwards, a breakwater by which the water flowing from the branchial cavity is kept away from the mouth and reconducted to the branchial cavity.

It then divides into two sections, a fore or branchial gut and a hind or hepatic gut, like the alimentary canal of the Balanoglossus, the Ascidia, and the Amphioxus. But the branchial gut, the one reminiscence of our fish-ancestors, is afterwards atrophied as such. The parts of it that remain are converted into entirely different structures. Transverse section of the head of a Petromyzon-larva.

In very moist air the store of water contained in the branchial cavity may hold out for hours, and it is only when this is used up that the animal elevates its carapace in order to allow the air to have access to its branchiae from behind.

If we appeal from adult anatomy to embryology the case becomes all the worse for us. Our ear is lodged in the gill-slit of a fish, our jaws are branchial arches, our hyoid bone the rudiment of this system of bones supporting the gills.