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In No. 4 we have an illustration of the tube-mouth or Solenostoma, one of the two known kinds of fish in which the female shows a sense of her position as a mother. The tube-mouth, as you can see at a glance, is a close relation of our old friend the seahorse, whose disguised and undisguised forms in Australia and the Mediterranean we have already observed when dealing with the question of animal masqueraders. Solenostoma is a native of the Indian Ocean, from Zanzibar to China. In the male, the lower pair of fins are separate, as is usual among fish; but in the female, represented in the accompanying sketch, they are lightly joined at the edge, so as to form a sort of pouch like a kangaroo's, in which the eggs are deposited after being laid, and thus carried about in the mother's safe keeping. No. 5 shows the arrangement of this pouch in detail, with the eggs inside it. The mother Solenostoma not only takes charge of the spawn while it is hatching in this receptacle, but also looks after the young fry, like the father stickleback, till they are of an age to go off on their own account in quest of adventures. The most frequent adventure that happens to them on the way is, of course, being eaten.

The nebulium lines are relatively strong in the central denser parts of the Orion and Trifid nebulae, but the hydrogen bright-lines are relatively very strong in the faint outlying parts of these nebulae. The planetary nebula B.D.--12 degrees.1172 is seen in the ordinary telescope to consist of a circular disc (probably a sphere or spheroid) of light and a faint star in its center. When this nebula is observed with a slitless spectrograph the hydrogen and nebulium components are seen as circular discs, but the hydrogen discs are larger than the nebulium discs. In other words, the hydrogen forms an atmosphere about the central star which extends out into space in all directions a great deal farther than the nebulium discs extend. The Wolf-Rayet star-planetary nebula D. M. + 30 degrees.3639 looks hazy in a powerful telescope, and when examined in a spectroscope the haziness is seen to be due to a sharply defined globe of hydrogen 5 seconds of arc in diameter surrounding the star in its center. Wolf and Burns have shown that in the Ring Nebula in Lyra the 3726A and the hydrogen images are larger as to outer diameter than the nebulium images, but that the latter are the more condensed on the inner edge of the ring. Wright has in the present year examined these and other nebulae with special reference to the distribution of the principal ingredients.

Sexual selection goes hand in hand with natural selection. From the very first I have regarded sexual selection as affording an extremely important and interesting corroboration of natural selection, but, singularly enough, it is precisely against this theory that an adverse judgment has been pronounced in so many quarters, and it is only quite recently, and probably in proportion as the wealth of facts in proof of it penetrates into a wider circle, that we seem to be approaching a more general recognition of this side of the problem of adaptations. Thus Darwin's words in his preface to the second edition (1874) of his book, _The Descent of Man and Sexual Selection_, are being justified: "My conviction as to the operation of natural selection remains unshaken," and further, "If naturalists were to become more familiar with the idea of sexual selection, it would, I think, be accepted to a much greater extent, and already it is fully and favourably accepted by many competent judges." Darwin was able to speak thus because he was already acquainted with an immense mass of facts, which, taken together, yield overwhelming evidence of the validity of the principle of sexual selection.

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