Lives of the Other Mollusks 49 



frequently eaten by peoples of the Mediterranean area and the Orient but to 

 a much lesser extent by Americans. 



In contrast to the speedy squid, the octopus is relatively a slow-moving 

 creature, although it can swim away at a fairly rapid rate by using the same 

 water-jet system of propulsion; it lacks the caudal fins of the squid. The 

 underside of the eight arms of the octopus are studded along their entire 

 lengths with cup-like disks or acetabula. When a sucker is pressed against 

 any smooth surface, the center is withdrawn to create a vacuum which en- 

 sures a powerful attachment. An octopus can "tentacle" along with remark- 

 able agility and at night may even take to short excursions out of water. I 

 have known of an octopus kept in a small aquarium in Bermuda to push the 

 lid off the top, crawl down the table and off the veranda in an attempt to 

 reach the ocean. It crawled more than a hundred feet toward the sea before 

 it succumbed and was attacked by ants. There have been many authentic 

 accounts of encounters with octopus on exposed tidal reefs, and a few ob- 

 servers state that the octopus can keep up with a man in a brisk walk. 



Even more astounding than the locomotive powers of the cephalopods 

 are their amazing displays of bright, glowing lights and color changes. The 

 shallow-water species have embedded in their skin chromatophores whose 

 expansion and contraction are controlled by the nervous system. Emotion, 

 excitation or response to the color of surrounding objects will effect the 

 color changes in the octopus. Among the deep-water squid, many of which 

 are phosphorescent, gorgeous underwater pyrotechnics are frequently dis- 

 played which far outshine the brightest of fireflies and glowworms. Specimens 

 of Lycoteuthis brought up from considerable depths and kept alive in chilled 

 water have had their photographs taken by their own light. The body looks 

 as if it were adorned by a diadem of brilliant gems. The middle organs of 

 the eyes shine with ultramarine blue, the lateral ones with a pearly sheen. 

 Those toward the front of the lower surface of the body give out a ruby-red 

 light, while those behind are snow-white or pearly, with the exception of 

 the middle organ which is sky-blue. Some squid have astonishingly com- 

 plex bull's-eye lanterns; others have mirrored searchlights. A species of Heter- 

 oteuthis is able to spurt out a luminous secretion from its funnel and the 

 jet of water following it draws out the bright globules into long, shining 

 threads. 



The sexes in the cephalopods are separate, except for two or three 

 isolated examples. In most of the species females are much more numerous, 

 the ratio of females to males being loo to 15 in some species of the Loligo 

 squid and 100 to 25 in some of the Octopus. The most outstanding feature 

 is the morphological differences between the two sexes. In the Argonauta 

 or Paper Nautilus, the females are 10 to 15 times as large as the males which 

 completely lack the beautiful shell used by females for storing eggs. The 



