A.  Cone shells and darts
	1.  Cone shells are snails that have a structure associated with
		food getting called a dart.  The dart is contained in a
		dart sac.
	2.  The snail lies in wait and when food items come close, the snail
		injects the dart into the prey's tissues.  The dart contains
		a poison that paralyzes the prey and the snail can thus use
		its radula to scrape pieces of flesh into its mouth.
	3.  Cone shells are highly sought by shell collecters, primarily
		because of the beauty of their shells.  Many shells have 
		extraordinary geometric patterns.  Some of these patterns
		are tessalations (like tiles in a floor that show a repeated
		patterns across the floor).
	4.  It is thought that these patterns do function as camouflage.  Even
		though the patterns stick out when the snail is removed from
		the reef environment, in the reef environment, the patterns
		blend in.
B.  Use of nematocysts by the Cnidaria
	1.  nematocysts of are structures (acellular) produced by the 
		cnematoblast, a cell.  There are three main groups of 
		nematocysts, poisonous, sticky, and tangly.  All work 
		essentially in the same manner in terms of being discharged
	2.  The nematocyst has a trigger, the cnidocil.  If this structure
		is touched, the nematocyst is fired.  It is not strictly
		tactile, as there also has to be a chemical in the vicinity
		the sensitizes the nemtaocyst to facilitate firing.  Often
		these chemicals are amino acids closely associated to prey
		species.
	3.  The extension of the nematocyst is inverted when unfired.  When
		discharge there is a change in osmotic relations in the 
		nematocyst and the "spear" is everted by increased pressure
		of the fluids in the nematocyst.  It then enlengthens and
		either is used to inject a poison in the prey, stick the 
		prey to itself if sticky, or entangle the prey.
	4.  A nematocyst can only be fired once.  Can't be reused or recycled.
		At the same time a cnematoblast can continue to make nemato
		cysts.  
	5.  Nematocyst are typically located in "batteries" of nematocysts.
		Thus many discharge when one is fired.
	6.  A few organisms actually use the nematocysts as a means of 
		protection.  One group of nudibranchs actually eat polyps
		of colonial hydroids, but don't cause the nematocysts to
		fire.  The nematocysts are passed through the gut wall
		and come to lie in the cerratia (finger like projections
		from the dorsal wall) and now are used to protect the
		nudibranch.
	7.  A few fish show a close relationship to some cnidarians, but
		seem to be unaffected by the nematocysts (eg., anemones
		and clown fish.)
C.  Urchins as herbivores
	1.  Graze on algae that grow either attached to substrate or that
		grow as a sheet on the substrate
	2.  Use an apparatus called  and "Aristotle's lantern".  Device
		consists of a series of supportive ossicles and five 
		teeth suspended from this framework.  Teeth are worked back
		and forth on the substrate to scrape the algae free.
	3.  Urchins have a complete digestive tract with an anus located
		at the end opposite the mouth.  Length of digestive tracts
		is somewhat related to the nature of the dietary intake.
		Since urchins are herbivores, their intestines are somewhat
		longish in order to allow time for the digestion of cellulose
		in their food materials.  Predators have much shorter tracts
		because proteolytic enzymes are very effective in breaking
		down proteins.
	4.  Urchins often graze in "herds" and leave an area free of algae
		after they have moved through.  
	5.  Urchin densities vary, but often can be as high as 100-300 urchins
		per square meter.  
	6.  Urchins are now being harvested from many areas because of the
		high prices they bring in Japan.  Apparently their gonads
		are thought to affect virility.
D.  Urchins, sea otters and giant kelps
	1.  Along the California coast there exists an interesting 
		relationship between urchins, otters and kelp.  The 
		otters prey on urchins, the urchins feast on kelp and the
		kelp provide a habitat for both groups.  With the 
		destruction of sea otters at the end of the 19th century,
		the main control over urchin populations was lost and as
		a result there was a destruction of the kelp forests (the
		urchins eat the kelp close to its base and as a result 
		the kelp break off and wash up on shore).
	2.  The otter is now a protected species and is making a comeback
		along the California coast.  As a result, so are the kelp
		forests.