Page:Popular Science Monthly Volume 20.djvu/437

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Rodents, Fossil and Living.—M. E. L. Trouessart, in attempting to explain the geographical distribution of living and fossil rodents from the point of view of the doctrine of evolution, divides the living rodents into four principal groups, or tribes: the cosmopolitan rats and their allies, which appear to find everywhere and under all circumstances conditions favorable to their existence and multiplication; the sciuromorphs (squirrels and marmots) and the lagomorphs (hares), almost exclusively of the northern hemisphere; and the hystricomorphs (porcupines, Guinea-pigs, and capybaras), which are now confined to the southern hemisphere. The study of the fossil rodents shows that these four types were neither as narrowly confined to particular regions nor, except the hares, as clearly defined and separated from each other as now. The types of the southern hemisphere were represented during the Miocene epoch in the north of both continents, and appear to have been driven south by glacial cold. The existing types of rodents first appear in the Eocene epoch, and by the side of them mammals with similar dentition, of which the chiromys of Madagascar may be regarded as the last survivor. Some of the mammals of the secondary epoch present the characteristic incisors of the rodents, with molars indicating a carnivorous or at least a more omnivorous nature than that of. the great majority of the modern rodents. Similar incisors are found in a number of insectivorous animals, as, for example, among the shrew-mice and several types of ungulates. We are thus led to conclude that this type of the rodents played at the beginning of the Tertiary period an important part in the history of a number of orders which have now become more specialized.


Whales and their Habits.—A correspondent of "Land and Water," who accompanied the Dundee whaling fleet to Davis Strait and Lancaster Sound last summer, mentions the change that has taken place in the geographical distribution of the Arctic whale. A century or two ago this animal was found everywhere north of the sixtieth degree of latitude, and extended many degrees farther south on the east coast of America. It abounded on the northern shores of Europe and the coasts of Iceland and Greenland, frequenting the islands of Jan Meyen and Spitzbergen in incredible numbers. Now it has deserted Spitzbergen and the north of Europe, it is becoming rare on the coasts of Greenland, and seems to be retiring farther into the unpenetrated recesses of the Polar Sea. Whalemen are not agreed as to whether the-animals are actually diminishing in numbers. Some believe that they are still as numerous as they were at the beginning of the century; others predict that the time of their total extinction is approaching. They are still sometimes seen in enormous numbers. Whales exceeding forty-seven and forty-eight feet in length are caught every year. Captain Deuchars, of the Dundee fleet, two years ago took a whale sixty-five feet long, the "bone" of which measured twelve feet ten inches, and which gave twenty-four tons of pure oil. The largest whale ever caught in Davis Strait, in 1849, had a "bone" fourteen feet long, and yielded twenty-seven tons of oil. The destruction of "suckers," or baby whales, which is considerable, may have something to do with the present decadence of the fishery. Whalemen think that no animal should be killed whose "bone" is not more than six feet long. Whales may live to a very great, but no one knows to how great, an age. Although dead ones are often found floating on the water, none are ever discovered that have died from natural causes. Whales are monogamous, and are much attached to their consorts. The correspondent who furnishes these facts tells of an animal which came back every day for a fortnight through great peril from the fleet to the place where its mate had been taken, regularly going over the course followed by her in her flight, looking for her. The animals sleep on the surface of the water, enjoy fine weather and sunshine, and are often seen at play on bright days. When they are together in large numbers, the water becomes covered with an oily exudation from their bodies, which has a sickly smell, and attracts flocks of "molly" petrels. They can live only on the most minute marine animals, for, though a whale's mouth "would hold a whale-boat, with all its crew, its gullet would be choked by a herring. When feeding, it swims through