A Synoptic Text-Book of Zoology for Colleges and Schools (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ...frogs, and toads. As a rule they pass through a larval stage in the water, and in the adult condition may live upon land, although many remain in the water all their lives. They are found in fresh water, never in salt. The body is covered with a soft, naked skin, except in one group, which possesses minute scales, but some of the extinct Amphibia were provided with well-developed bony plates in the integument. Some extinct species were gigantic in size; in one the skull alone was over a meter and a half long. The skin contains numerous glands, which by their secretions keep it moist while out of the water. In some species the secretion is poisonous to other animals. The outer layer of the skin is shed periodically. Many Amphibia which possess tails, such as the hellbender and mud puppy of our Central states, are strikingly fishlike in appearance. There is an unpaired fin on the dorsal side, continuing about the diphycercal tail and along the posterior part of the ventral side, like the median fin of the Dipnoi, the true eels, and some other fishes. But this fin is never provided with skeletal supports, or fin-rays, as in the fishes. The great difference externally between such Amphibia and the fishes is found in the paired appendages, which here are never fins, but pentadactyl extremities, or legs. As a rule there are two pairs of these, anterior and posterior, or pectoral and pelvic; but in a few cases only the anterior pair is present, and in a few both pairs are absent. These appendages are provided with an internal bony skeleton, and the arrangement of the bones is on the same plan in this and all the higher groups of Vertebrata; Fig. 308. Rana temporaria, the common European frog. A, dorsal aspect of skeleton; on the left half the...