The male octopus goes to an extreme in this 

 final step of an elaborate courtship. He drops off the 

 tip of the arm with its load of sperm bags deep in his 

 mate's mantle cavity. Early observers found the still- 

 living arm tips anchored securely there and con- 

 cluded that they were parasitic worms entirely dif- 

 ferent from all others known because of the scores 

 of sperm-filled cavities. To these "worms" the name 

 Hectocotyhis was given (hecto, a hundred, kotyle. a 

 hollow vessel). When the true situation was discov- 

 ered, the word came to be used as an adjective de- 

 scribing the peculiar arm as being the "hectocoty- 

 lized" one. 



The body of an octopus is rounded or saclike, usu- 

 ally with no fins (Plates 76-80). Ordinarily the ani- 

 mal crawls about on its flexible arms. But if fright- 

 ened, it ejects water from the capacious mantle cavity 

 through a narrow nozzle-like siphon. The water 

 spurts forward, and the animal darts backward by 

 jet propulsion. 



The female octopus cements her eggs to a rock or 

 other firm support. Some species attach them like 

 punching bags, singly on short stalks. Others include 

 a whole series of eggs in a slender string of jelly and 

 affix the end of the string. For as much as three 

 months, the mother octopus may stand lonely vigil 

 over her developing offspring, not forsaking them 

 even to find food. With her sucker-studded arms she 

 polishes the outside surfaces of the egg coverings, 

 keeping them free of dirt and fungus growths. Some 

 kinds of octopus use their siphons as a sort of hose, 

 sending jets of water among tlie egg strings and flush- 

 ing out any minute particles that might contaminate 

 them. 



Squids, by contrast, lay many smaller eggs in cigar- 

 shaped masses of jelly attached to the bottom and 

 then go off, leaving the "dead man's fingers" to fate. 

 Very few animals actually attack squid eggs, which 

 suggests that they have an unpleasant flavor or toxic 

 nature. When octopus eggs are left unattended 

 through the death of the parent, fungi soon smother 

 them. 



Squids get far more effective use of jet propulsion, 

 since their bodies are more cylindrical, tapering to 

 a point and hence affording better streamlining 

 (Plates 72 and 73). On each side the body bears a 

 pair of horizontal muscular fins under exquisite con- 

 trol. With their help alone, a squid can hover, swim 

 forward or back, or turn about sharply. Sometimes it 

 uses the flexible siphon tip to direct a jet of water to 

 rear or downward or to one side instead of forward, 

 and gains an extra lift in this way. 



Squids tend to hunt in packs, darting by jet pro- 

 pulsion through a school of fish and seizing victims 

 by the head. Octopuses, on the other hand, are more 

 solitary and bottom-dwelling. They may stalk a crab 

 or wait for it to come within snatching distance. Al- 



The sea butterfly ( pteropod ) Creseis i,s a delicate 

 little frec-.SNvimming snail of the open ocean. It ex- 

 tends a pair of wing-like expansions of the foot from 

 the larger end of the thin shell and flits through the 

 water in company with many others of its kind. The 

 specimens shown were dredged from Bikini lagoon 

 in the South Pacific. (Fritz Goro: Life Magazine) 



ways, however, they seize it from behind and thus 

 avoid the crab's claws. 



The extra two arms of squids, beyond the eight 

 characteristic of octopuses, are considerably longer 

 than the rest and are used in grasping prey. In the 

 giant squid Archileuthis prince ps of moderate depths 

 in colder oceans, these prehensile arms may be 30 

 feet long on a 15- to 18-foot body as much as 5 feet 

 in diameter. 



Archileuthis is a real sea monster, the largest of all 



Large clam. Tridacna, wedged among coral on Great Barrier Reef. The giant 

 species of Tridacna may be 4 feet long and weigh up to five hundred pounds. 

 (Fritz Goro: Life Magazine) 



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