Colouration of Invertebrata. 87 



divide the chambers, though, as is often the case, they are generally 

 more numerous than the septa. 



The naked Cephalopoda, or cuttle-fishes, often possess a distinct 

 dorsal stripe, and when our views were first brought before the 

 Zoological Society, this fact was cited as an objection. To us it 

 seems one of the strongest of favourable cases, for these animals 

 possess a sort of backbone the well-known cuttle-bone and hence 

 they have a dorsal line. 



Some shells, as Margarita catenata, have a chain-pattern, and in 

 this case the action of the pigment cells takes place at regular and 

 short intervals. Others, as Mactra stultorum, the stencilling forms a 

 series of lines and spots, generally enlarging into rays. 



The whole subject of the decoration of shells deserves much 

 more time than we have been able to give to it as yet. 



