Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/672

Rh 634 ALPS in the lake of Lucerne. The most esteemed are those of the trout and salmon tribe, whose specific differences have not yet been fully investigated by ichthyologists. First in rank is the saibling (Salmo salvellinus), which flourishes in lakes between 2000 and 4000 feet above the sea, and occasionally extends to those of the Alpine region between 6000 and 7000 feet. The fish of the northern side of the Alps are fully described in Siebold s Sussivasser-Fische Mitteleuropas. Those of the waters running to the Mediterranean have not been so fully investigated. Two or three peculiar species have been found in the lake of Geneva. In some of the Lombard lakes, the agone, a small fish of the herring tribe (Clvpea finta), is a much esteemed article of diet. rtc-, In the classes hitherto noticed the number of species a - peculiar to the Alps is very small. This rule is reversed among the Invertebrata, especially as regards the Articu- lata and Mollusca. The number of insects is veiy great, ^and a considerable proportion extend to the limit of per- petual snow. Oswald Heer has pointed out several pecu liarities in the insect fauna of the higher Alps. In ascend ing from the mountain region the proportion of the carnivorous tribes rapidly increases, and the families that feed on living vegetable matter either disappear or are much reduced in numbers. Beetles and other insects either lose their wings in the upper region, or are represented by allied wingless species. Along with the tendency to lose the power of flight, a diminution of brilliancy of colour appears, the prevailing hues being black or dingy grey. These peculiarities are to be explained by the fact that in the upper Alpine zone most insects live under stones, and the power of flight generally proves injurious to animals liable to be carried by the wind and upward air-currents over the snow-fields, whence they are unable to return. This is often seen to occur to butterflies and a few moths, which ascend as far as the highest flowering plants. The snow-fields and glaciers are not devoid of insect life. Several species of snow-flea have been detected ; and further observation will probably bring to light other minute animals living in the pools that form on the surface of glaciers, or on the snow-beds, although their activity is often interrupted by the freezing of the surface. The Arachnida are eminently characteristic of the fauna of the high Alps, where they abound both in species and individuals. Spiders ascend to the utmost limit of vegeta tion, and are even to be found on the bare rocks that rise out of the snow up to a height of 11,000 feet. Although most of the orders of Articulata are repre sented in the Alps by numerous forms, these are far out numbered by the total number of European species of that class ; but among land and fresh- water Mollusca the pro portion is reversed, and as many as seven-eighths of all the species known in middle Europe, and a large propor tion of those of the Mediterranean region, have been found in the Alps. Still more remarkable is the large propor tion of endemic species. In the important group of the Heliceae fully one hundred species, or four-tenths of the whole number, are peculiar to the Alps. Between thirty and forty species only have been found in the Alpine zone, and of these but five Vitrina diaphana, V. glacialis, Helix glacialis, II. fcetens, and Vertigo Charpentieri attain the upper limit of vegetation. The Annulosa and Radiata of the Alps, so far as they are known, do not offer any points of special interest; and the study of the minute organisms, which have been proved to exist as high as 12,000 feet above the sea, is still in its infancy.
 * -a of In. describing the several regions which are found in

Alps, ascending from the low country to the snow-clad summits of the Alps, and whose existence is due to climatal differ ences, it was necessary to refer to the characteristic vege tation of each zone, inasmuch as this affords the chief apparent distinction which climatal conditions impress on the earth s surface. The most cursory observation suffices to show that within each of the zones thus broadly sketched out there exist marked differences in the vegetable popula tion, so that a comparison of the local floras in two spots possessing a similar climate as regards temperature may exhibit but few points of agreement along with many marked contrasts. This partly depends on external con ditions, of which the most important are differences in the amount and distribution of moisture in the air and the soil, and differences in the composition and state of aggre gation of the soil itself. But a more important element in determining the flora of any particular district depends upon the causes which have operated throughout the whole period since it has become dry land to facilitate migration for certain species, and to impede it for others. The sub ject of the distribution of Alpine plants, so far as regards the eastern half of the chain, has been very well discussed in an essay by Dr A. Kerner in the 1st vol. of the 2d edit, of Schaxibach s Deutsche Alpen, although some of the con clusions of the writer may not bear careful criticism. lie divides the natural floras of the Alps into four named respectively Arctic, Baltic, Pontic, and Mediterranean, the term Baltic referring to the region that includes Germany, Southern Scandinavia, and North- Western Russia; while Pontic comprehends the region north and west of the Euxine the northern provinces of Turkey and the whole space between the Carpathians and the Crimea. It does not appear that the writer holds that the plants existing in the Alps have actually migrated to their present homes from the geographical regions corresponding to the above deno minations, but merely that they belong to the types of vegetation characteristic of each of them. It must be borne in mind that the Alps, and especially the mountain and sub-Alpine regions, produce a large number of peculiar forms, many of which have no near allies in the other mountain regions of Europe, while at the same time the differences are seldom so wide as to place these in distinct generic groups ; and it seems quite inadmissible to suppose that the flora has been altogether formed by colonisation from surrounding districts. No space can be here found for details, but it may broadly be said that while the highest zone of all, lying close to the limit of permanent snow, exhibits throughout the whole chain an approach to uniformity, several of the most conspicuous species being common to this and to Arctic flora, the zone immediately below this, as well as those lower down, shows a large admixture of quite distinct elements. This is especially true of the southern slopes. In truth, but a very few of the well-marked endemic species of the Alps are confined to the north side of the main chain. A considerable number are common to both slopes, and a still larger pro portion are restricted exclusively to the southern side. Of the larger groups which are represented in the Alps by numeroiis well-marked endemic species, the genera Alsine, Androsace, Arabis, Campanula, Crcpis, Gentiana, Pedicu- laris, Primula, and Saxifraga may be especially noted. Without attempting to enter into details, it may be said that, along with a general Alpine flora, which extends throughout the entire chain, there are three large districts where, along with species common to all, we find a con siderable number of others cither absolutely local and endemic, or else representative in the Alps of the floras of other distant mountain groups. Only a few of the more remarkable species characteristic of each can be cited. The West Alpine Flora is found in Dauphine, South Savoy, and Western Piedmont, as far north as the group of the Graian Alps. In the following list of the more remark-