Blackwall observed nine moults in _Tegenaria civilis_, a spider that lives several years. Many species, and among them some of the largest, live only one year, hatching in the winter, leaving the cocoon in early summer, and laying eggs and dying in autumn. Other species seem to require two years for their growth; hatching in summer, passing their first winter half grown, growing up the next summer, but laying no eggs till the second spring. Some species are found adult at all seasons, and may live several years. After spiders have passed their second moult, they usually live in the same places, and follow the same habits, as the adults. The running spiders live usually on the ground, often near water, but some kinds in the hottest and dryest places. A few species live near water, and are accustomed to run about on its surface, without becoming wet. The _Theridiidæ_ almost all live in the shade, and always upside down in their webs. Some species live always in caves; and one in the deepest part of the Mammoth Cave has no eyes. Some spiders live only on high mountains, never appearing below the tree line. Some species seem to prefer certain kinds of plants. The horizontal branches of spruces, for instance, are particularly convenient for the webs of some species of _Theridion_. The water-spider, that builds its nest and lives on water-plants, has been already mentioned, and also the _Argyrodes_, that makes its home in the webs of other spiders. During winter immense numbers of spiders that have spent the summer under stones, in webs, and on plants, hide away among fallen leaves, and there live through the coldest and wettest weather, ready to move on the first warm day. During a thaw they often come out on the snow in great numbers. Several house spiders have probably been imported, like rats, and are found all over the world; while other most common species never spread beyond the countries where they are most abundant. BOOKS ABOUT SPIDERS. CLASSIFICATION.—Thorell’s “Genera of European Spiders,” in “Acta Regiæ Societatis Scientiarum Upsalensis,” 1869, and Thorell’s “Synonymes of European Spiders,” contain a complete history of the classification of the spiders of Northern Europe, with references to all the descriptions of genera and species, and remarks on the use of names and groups by different authors. The great resemblance between the European and North-American spider faunæ make these the most useful books for American students. Simon’s “Arachnides de France,” a work not yet completed, describes all the spiders in France, and refers to descriptions of the other European species. It contains tables by which the genus and species to which any spider belongs can be found by the use of a few prominent characters.