Lastly, How fondly some writers dwell upon the many touching instances of affection apparent in the feathered tribe, and narrate how carefully and how skilfully the little wren, for example, builds its nest, and tenderly rears its young. I have often watched the common fowl, and admired her maternal anxiety to make her outspread wings embrace the whole of her unfledged brood, and keep them warm. The cat, too, exhibits this characteristic love of offspring in a marked degree. She will run after a rude hand that grasps one of her blind kittens, and, if possible, will lift the little creature, and run away home with it in her mouth. Now, whether we look at the singular skill of the bird building its nest, the hen sitting near and protecting its brood, or the cat grasping her young in its jaws, and carrying them home in safety, we shall find that all these charming traits are wonderfully combined in one of the humblest members of the finny tribe, viz., the common stickleback,--the little creature that boys catch by thousands with a worm and a pin,--that lives equally content in the clear blue sea or the muddy fresh water pool. The author now finds that he has been much too prolix in these preliminary observations to leave himself space for a lengthened explanation of his reasons for again intruding upon the public. These are neither original nor profound. But he cannot help expressing an earnest hope that he may get credit from old friends, and perhaps from some new, for wishing to show that the book of nature is as open as it is varied and inexhaustible; and that, however jealously guarded are many of the great secrets of organization, a knowledge of some of the most familiar objects tends to inspire us alike with wonder and with awe. CHAPTER II. A Glance at the Invisible World. 'There is a great deal of pleasure in prying into this world of wonders, which Nature has laid out of sight, and seems industrious to conceal from us.... It seems almost impossible to talk of things so remote from common life and the ordinary notions which mankind receive from the blunt and gross organs of sense, without appearing extravagant and ridiculous.'--ADDISON. II. It is hardly possible to write upon marine zoology without either more or less alluding to those many objects, invisible to the naked eye, which call for the use of the microscope; and it seems equally difficult for any one who has been accustomed to this instrument to speak in sober terms of its wonderful revelations. The lines of Cowper, as the youngest student in microscopic anatomy will readily acknowledge, present no exaggerated picture of ecstasy:-- 'I have seen a man, a worthy man, In happy mood conversing with a fly; And as he through his glass, made by himself, Beheld its wondrous eye and plumage fine, From leaping scarce he kept for perfect joy.'