OCCURRENCE OF TRICLADIDA 



33 



gill-plates, upon which the eggs may be found in considerable 

 numbers. One species, Syncoelidium pellucidum, possesses a pair 

 of problematical organs in the hinder part of the body, opening 

 to the exterior ventro-laterally by a couple of chitinous mouth- 

 pieces, but having no connexion with the genital ducts. 1 



Occurrence and Distribution of Land Planarians. The 

 terricolous Triclads or Land Planarians are the most interesting 

 division, of the group. Some forms, such as Bipcdium Jcevjense, 

 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 colora- 

 tion, though somewhat variable, is an important specific char- 

 acter. Its significance, however, is not clearly understood. The 

 colours may be a warning signal, as some Geoplanci at least are 

 disagreeable to the taste of man and some birds 2 ; but since 

 Land Planarians are largely nocturnal animals, living by day 

 under logs, banana leaves, and in other moist and dark situa- 

 tions, this explanation is clearly insufficient. Two Geoplanci 

 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. 3 

 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 Plan- 

 arians, in addition to possessing offensive properties, the mucus 

 is so copious in amount and hardens with such rapidity, that 



1 Wheeler, Journal of Morphology, vol. ix. 1894, p. 167. 



2 Dendy, Trans. Roy. Soc. Victoria 1890, p. 65 ; Id. Austral. Assoc. Brisbane, 

 1895, "Presid. Add. to Sect. D," p. 15. 



3 Darwin, Ann. and May. Nat. Hist. vol. xiv. 1844, p. 241. 



VOL. II D 



