A.  Porifera
	1.  Collar cells function in a manner similar to that of protists.
	2.  Particles get caught on the collar, are then engulfed and pass
		through rest of cytoplasm as food vacuoles.
		a.  Collar is actually a series of microvilli that are fused
			into a cylindrical membrane
		b.  Flagella serve to cause a current that brings particles
			into contact with the collar
	3.  Contents of food vacuoles are subjected to enzymatic breakdown
		as they circulate through the cytoplasm of the choanocyte.
	4.  Materials are absorbed out of the food vacuoles.  Some materials
		are passed on to the other cells, porocytes, pinacocytes, etc.
		that do not have direct feeding functions.
B.  Cnidaria
	1.  Two general processes take place
		a.  extracellular digestion--secretion of enzymes by the cell
			into a lumen
		b.  intracellular digestion--phagocytosis of particles by 
			cells with subsequent breakdown in the cytoplasm of
			the engulfed materials.
	2.  Gastrovascular cavity functions in two ways; as a hydrostatic
		skeleton and as a digestive tract.  There are some 
		difficulties as when mouth is opened for the insertion of 
		food materials, gastrovascular fluid can leak out.
	3.  Cells lining the cavity are columnar epithelial cells.  The
		lumen end has flagellae.  The creatures catch microcrustaceans
		and put them into the gastrovascular cavity.  The cells then
		secrete enzymes which partially digest the whole animals into
		smaller chunks.  When the chunks are small enough for phago-
		cytosis, the gastric cells engulf the particles and intra
		cellular digestion takes place.  The food vacuoles again,
		circulate through the cytoplasm.  Materials absorbed by
		the cytoplasm are passed on to the other cells in the 
		organism
	4.  The digestive functions are pretty much similar in the rest of
		the cnidaria.  The one additional feature is that many 
		cnidaria contain photosynthetic symbionts, which also supply
		energy to the individual or colony.
C.  Ctenophora (cten= comb)
	1.  This phylum is similar to the cnidaria in some ways; two cell
		layers and a mesoglea.  Only a few have nematocysts, but most
		have colloblasts, structures somewhat similar to nematocysts.
	2.  Two classes, one with tentacles and the other without.  Most are
		spherical and contain eight rows of ciliated combs down the
		lateral sides of the organism.
	3.  Often travel in groups and feed very effectively on plankters.
		Because the plankton occurs in patches, the comb jellys
		essentially cut a swash through a "cloud" of plankton.
	4.  Those with tentacles use the tentacles to bring food particles
		to the mouth where they are ingested and handled in a manner
		similar to that of the cnidaria.
D.  Platyhelminithes
	1.  Class Turbellaria has a gut.  Two examples are the freshwater
		triclads which have a three forked gut (one forward, two
		backwards) and the polyclads which have multiple forks.
	2. The guts are multibranched which increases the surface area. 
		Animals may produce some enzymes which perform extracellular
		tasks.  Materials are taken into the digestive system by 
		a muscular pharynx where cells lining the digestive tract
		engulf materials and complete the process intracellularly
	3.  The trematodes also have a branched gut, much simpler in 
		structure.  May be related to the parasitic nature of their
		life style.
	4.  The flukes have suckers to hold on to the host tissues, one 
		around mouth/pharynx and another on the ventral surface of
		the body.
	5.  Materials are taken into the gut where intracellular digestion
		takes place.
	6.  Parasitic cestodes lack a gut.  Living in the digestive tract,
		most of the materials are pre-digested by the host.  One
		problem is to avoid digestion by the host.  This is somewhat
		of a paradox as to absorbed food materials you need a thin
		epithelium, but to avoid digestion you need a thick body 
		wall covering.
E.  Two other phyla, Nemertina and Nematomorpha.
	1.  Both show a complete gut, ie., mouth and anus.
	2.  Nemertines are related to platyhelminthes and are longer and
		ribbon-like with a structure in the region of the mouth
		that can be shot out into prey items.
	3.  Nematomorphans perhaps more closely related to nematodes.  Adult
		does not feed, and only performs reproductive duties.  Larval
		stage often found in insects and does feed.