74 MOLLUSCA. 
upon the bottom among the rocks. The body (Fig. 78) 
is a simple sac, from which radiate eight sucker-lined 
arms. They are very powerful, and when enraged waves 
of color pass over the skin in rapid succession. When 
attacked they eject a cloud of ink, and under its cover 
crawl away, passing through incredibly small holes, and 
so mimicking the colors of the bottom that an experi- 
enced eye is necessary to detect them. ‘They feed upon 
crabs and other animals, and are mainly bottom animals, 
though some species have web-like membranes between 
their eight arms enabling them to swim. Each egg of the 
octopus is inclosed in a thin, transparent, oval case, and 
attached by a stalk with several hundred others to the 
bottom ; sixty species are known. 
VALUE.—The fisheries are important to the Chinese. 
Argonaut (Argonautide)—The Cephalopods of this 
family are often incorrectly figured with sails raised in the 
air. The shell is symmetrical and of great delicacy and 
beauty. The animal rests in it, the upper or dorsal pair 
of arms being developed at their tips into membranes that 
are thrown back over the shell (Fig. 79), holding the 
Fic. 79.—Argonauta argo.—A, female with the expanded arms in their nat- 
ural position, embracing the shell, 4; @, the other six arms; a, the 
funnel. 2, suckers. 
Argonaut in. The broad tentacles also contain the shell- 
secreting glands. The shell is likewise the nursery, the 
eggs being attached within it and carried about. The 
male secretes no shell, and is extremely small. They are 
deep-water animals, and crawl about upon the bottom 
