UNSEGMENTED SCHIZOCOELS 



223 



octopuses. All reliable witnesses indicate that no 

 matter what size the octopus, it always tried to leave 

 when encountered by man. The fear and tales of 

 dangerous encounters appear to have come from 

 sailors who enjoy terrifying land-lubbers. Giant 

 squids, the largest known invertebrates, reaching a 

 body-tentacle length of over 50 feet, could definitely 

 be dangerous to humans; but they are deep sea forms. 

 The tales of giant squids attacking and destroying 

 boats are probably additional sea yarns for the land- 

 locked individuals' benefit. 



Except for two or three examples, the sexes of 

 cephalopods are separate. Females seem to be four to 

 seven times as numerous as the males in the different 

 species. There is no free-swimming larval stage as 

 found in other mollusks. The egg hatches into a 

 miniature adult. Octopuses care for and protect the 

 developing eggs, and it seems necessary for the female 

 to wash or clean the eggs during development to pre- 

 vent their loss from bacterial infection. The parent 

 appears to remain with the eggs during the entire 

 period of development, the adult never leaving even to 

 feed. In most cephalopods the male is characterized 

 by one flattened arm which is further modified for 

 the transfer of sperm to the female. 



Cephalopods have long been used by man as a 

 source of food. Prejudice now causes many people 

 not to eat octopuses, which are every bit as tasty as 

 many "acceptable" mollusks. Cuttlebone for the 

 birdcage is a representation of the cephalopod in- 

 ternal shell. The shells of nautili, mostly South 

 Pacific animals not found in United States waters, are 

 sought for their ornamental value. There is little 

 about the group that one could possibly construe as 

 being detrimental to man. 



Figure 13.10 Echiuroid types: above, Urechis, the innkeeper, marine; 

 below, Boneliia, o marine genus in which a sexless stage becomes a 

 parasitic male if it contacts o female, or becomes a female if no male 

 is found. 



constructs a U-shaped burrow in which it traps 

 microscopic food by pumping water through the 

 mucous funnel it secretes in its burrow. This inn- 

 keeper usually has a segmented worm, a crab, and a 

 small fish as tenants in its burrow. The tenants 

 apparently either live on the scraps that the inn- 

 keeper misses, or perhaps steal food from the inn- 

 keeper. 



ECHIUROIDEA (Innkeepers and allies) 



Diagnosis: symmetry bilateral; unsegmented; 

 schizocoelous; gray, reddish, or yellowish, cylindrical 

 creatures from 1 to 18 inches long; superficially re- 

 semble priapuloids, aschelminths, and sipunculoids, 

 but the anterior proboscis is either spoon-like or 

 thread-like and long; the proboscis is contractile, but 

 cannot be withdrawn into the body; marine bur- 

 rowers; sexes separate, trochophore producers (Fig- 

 ure 13.10). 



These worms live in mud or sand in shallow coastal 

 waters. Perhaps the most interesting of them is the 

 innkeeper (Urechis). This intertidal California species 



SELECTED READINGS 



Abbott, R. T., 1954. American Seashetb. D. Van Nostrand 



Co., Princeton, N.J. 

 Hyman, L. H., 1959. The Invertebrates. Vol. 5: Smaller 



(.'oelomate Groups, McGraw-Hill Book Co., New York. 

 Morris, P. A., 1951. .4 Field Cuide lo the Shells of our Atlantic 



and Gulf Coasts. Houghton Mifflin Co., Boston. 

 . 1952. A Field Guide lo the Shells of the Pacific Coast 



and Hawaii. Houghton MifHin Co., Boston. 

 Morton, J. E., 1958. .Mollusks. Hutchinson University 



Library, London. 

 Pilsbry, H. A., 1939-1946. Land Mollusca of .S'orth .America. 



2 vols., each in 2 parts. Acad Nat. Sci., Philadelphia. 



*See also p. 212. 



