OCCURRENCE AND DISTRIBUTION OF LAND PLANARIANS.—The terricolous Triclads or Land Planarians are the most interesting division of the group. Some forms, such as _Bipalium kewense_, attain large dimensions, being usually 6 to 9 inches in length, and specimens fully extended have measured 18 inches. Their bodies are frequently banded or striped with brilliant colours. _Geoplana coerulea_ Mos. has a blue ventral surface and is olive green or dark Prussian blue above. _G. splendens_ Dendy, is marked dorsally by three stripes of emerald green alternating with four dark brown longitudinal bands. The mode of coloration, though somewhat variable, is an important specific character. Its significance, however, is not clearly understood. The colours may be a warning signal, as some _Geoplana_ at least are disagreeable to the taste of man and some birds[46]; but since Land Planarians are largely nocturnal animals, living by day under logs, banana leaves, and in other moist and dark situations, this explanation is clearly insufficient. Two _Geoplana_ have been noticed by Mr. Dendy which seem to be protectively coloured. _G. triangulata_ var. _australis_ occurs abundantly in the beech forest in the South Island of New Zealand, and its brown back and yellow or orange ventral surface match the leaves around its haunts. _G. gelatinosa_ again looks like a mere slimy patch on the rotten bark where it is found. In arid districts, during the dry season, Land Planarians burrow in the soil and form a cyst, in which they lie coiled up, after the manner of earthworms.[47] The glutinous investment of their delicate bodies forms a moist medium in which the cilia covering the body (and especially the ventral surface) may constantly and evenly vibrate, and by which they adhere firmly to their prey. In some tropical Planarians, in addition to possessing offensive properties, the mucus is so copious in amount and hardens with such rapidity, that {34}these Triclads may creep over bridges of it, and may even be blown from one stem or branch of a plant to another, hanging at the ends of their threads.[48] [Illustration: FIG. 15.—Some Land Planarians found in Europe. A, _Bipalium kewense_ Mos. × ⅓ (after Bergendal); B, _Rhynchodemus terrestris_ O. F. M., × 2; C, _Geodesmus bilineatus_ Metsch., × 2½ (after Metschnikoff). _mr_, Region of mouth; _gp_, region of genital pore.]