482 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
epidermis. When the chromatophores are thus expanded, 
the colour of the animal is very deep—this occurs when 
Eledone is excited in some way. When the radial 
muscles relax, the chromatophore contracts and the 
animal becomes pale, as when frightened. In the 
normally quiet state the chromatophore is in a state of 
tension, and is shaped like a biconvex disc (II, Chr.). In 
this stage it is in a semi-expanded condition, the 
contractile tendency of the two elements being equally 
balanced. However, the cell is constantly varying 
slightly in shape, as one or the other of the forces gets 
the upper hand; and so the chromatophore exhibits 
incessant slight tremulous movements. Hence when 
watching Eledone in an aquarium, one is struck by the 
constantly varying colour of the skin. 
Harting, Blanchard and Girod agree that the vesicle 
is of ectodermal, and the girdle of mesodermal origin, but 
they consider that all motion on the part of the 
chromatophore is due to the amoeboid movements of the 
vesicle itself, while the radial fibres are connective tissue 
only. \ 
Again Chun, who worked on the chromatophores of 
Bolitaena, a deep sea form, disagrees with both these 
views. In Bolztaena the chromatophore arises as a single 
ectodermal cell which sinks down into the dermis. The 
nucleus now divides repeatedly, while the cell throws out 
about 18 pseudopodial processes, in the equatorial plane 
parallel to the epidermis. At the base of each process is 
found a corresponding nucleus, which has originated as 
above. Later it is found that this girdle of processes has 
become differentiated into a ring of triangular muscular 
strands, whose contraction serves to expand the 
chromatophore. A second muscular region becomes 
differentiated round the periphery of the cell, and this 
opposes the radial tracks, tending to contract the 
