ELEDONE. 483 
chromatophore. Hence Chun in Bolitaena derives the 
vesicle and the contractile apparatus wholly from one 
ectodermal cell. He has also traced the nerve supply of 
the chromatophores. For instance, the pallial nerve has 
several purely chromato-motor strands which run 
outwards to the external epithelium of the mantle, and 
there divide up ultimately into fine terminal nerves, one 
of which supplies each radial muscular strand, entering 
it at the narrow distal end. These nerves control the 
movements of the chromatophores, and therefore if the 
pallial nerve be severed the movements of the chromato- 
phores on the corresponding side of the mantle cease. 
This method of origin, which Chun has described, may be 
peculiar to the chromatophores of Bolztaena, and 1s 
difficult to reconcile with the account given by Rabl and 
others. 
In Kledone the pigment granules are very minute 
’ and of a reddish-buff colour. As in all Cephalopods, the 
motion of the chromatophores continues some time after 
death. 
Iridocysts.— These are light-reflecting cells embedded 
in the dermis below the chromatophore layer. They are 
uninucleate flattened cells, each of which contains two 
rows of thin fibrillar laminae arranged parallel to one 
another and reflecting the light, and so giving rise to the 
peculiar metallic iridescence noticed in the integument. 
TT.—ExtTEeRNAL ORGANISATION. 
The body may be divided into two regions—an 
anterior cephalopedal mass, and a posterior mass, or 
visceral dome, covered by the mantle. 
As in other Octopoda these two regions are united 
dorsally by a thin superficial sheet of muscles. 
Externally the two regions of the body cannot be 
