Environmental considerations; invertebrate classification; the protozoan protists; the poriferans and placozoans; the cnidarians; the platyhelminthes; two possible flatworm relatives - gnathostomulids and mesozoans; gnathostomulids and mesozoans; introduction to the hydrostatic skeleton; the nemertines; the nematodes; three phyla of uncertain affiliation - nematomorpha, acanthocephala and priapulida; the rotifers and three related phyla; the molluscs; the annelids; echiurans and sipunculans - likely annelid rivers; the pogonophorans; the anthropods; two more phyla of uncertain affiliation; tardigrades and onychophorans; the lophophorates (phoronids, brachipods, bryozoans) and entoprocts; the echinoderms; the chaetognaths; the hemichordates; the nonvertebrate chordates; invertebrate reproduction and development - an overview.
