The animals of the barnacles (Pentalasmis) attached to these shells assume their purple colours, while the shell remains nearly pure white.

This afternoon we caught an animal (Glaucus, Illustration 10) I had not before seen.  It seemed to represent the order reptilia in the Mollusca, being sluggish in movement, its eyes distinct, sensitive to the touch, its head much resembling a lizard in appearance, and having a very strong unpleasant smell when taken out of the water.  During the hour I observed it in a bucket it remained sluggishly floating on the top, and occasionally swimming by moving its arms slowly along the surface.  The first three that I saw pass the vessel I imagined to be feathers floating on the water.

Its description is as follows: 

Length from head to tail, a c 1.8 inches. 
Length from head to root of tail, a b 0.85 inches. 
Length from head to first arm 0.2 inches. 
Length from head to second arm 0.45 inches. 
Length from head to third arm 0.7 inches.

1st arm. 
From centre of back to end of round part, d e 0.3 inches. 
From e to the end of short tentacula, e f 0.3 inches. 
Ditto to long ditto, e g 0.75 inches. 
Diameter of round part and attached tentacula 0.4 inches.

2nd arm.  From centre of back to end of tentacula. 0.4 inches.

3rd arm, do. do. 0.25 inches.  Breadth of body between the two first arms 0.13 inches.  Thickness 0.25 inches.

General colour of body, indigo blue, of a darkish tinge; down the centre of the back a white streak, terminating at the root of the tail; sides blue, tail blue, quite white underneath, its belly altogether resembling that of a frog; tail tapering to a point.

1st arm. 26 tentacula attached to the rounded paddle-shaped part of this arm, the centre tentacle more than twice the length of the others.  These tentacula were so delicate that at the slightest touch they fell off.  Those nearest the body were so small as to be almost imperceptible, gradually increasing in length as they approach the centre, and then decreasing to the other side.  Centre of paddle-shaped part white, tentacula blue and white, fringed with dark blue at the extremity.

2nd arm. 18 tentacula to this, centre ones the largest.  Same colour as first arm.

3rd arm. 12 tentacula, not forming such a regular circle as on the two first arms, and apparently issuing directly from a very short limb attached to the body.

The general appearance of the skin was that of a frog.  It had the power of contracting itself considerably.

Caught a slug-like animal (Holothuria) this evening, or rather more closely resembling a caterpillar.

Length from head to root of tail 0.7 inches. 
Length of tail (or rather gelatinous protuberance) 0.25 inches. 
Breadth (broadest part at root of tail) 0.22 inches. 
Narrowest part (near head) 0.15 inches. 
Length of head 0.12 inches.