23° 



AN INTRODUCTION TO ZOOLOGY. 



Some of the Cuttle-fish are phosphorescent in the 

 dark. Some have an arrangement of pigment cells, 

 called chromatopliores, in the skin, by the altera- 

 tion of the shape and shade of which they change 

 colour. Many animals have something similar, e.g. 

 the chameleon. In the Cuttle-fishes, the nerves which 

 govern the chromatophores are connected with the 

 optic ganglion. It should he added that the Cephalo- 

 poda, like the Gasteropoda, possess a lingual ribbon 

 armed with teeth. 



Fig. 80. — Dibranchiate Cephalopods. ^, A Decapod Cuttle-fish, the Squid 

 (Loltgo i;ulga™), audits bone. B^ Shell of the female of the Paper Nautilus 

 (.Argonauta ox^iS]. 



