1 Environmental Considerations
2 Invertebrate Classification and Relationships
3 The Protozoan Protists
4 The Poriferans and Placozoans
5 Introduction to the Hydrostatic Skeleton
6 The Cnidarians
7 The Ctenophores
8 The Platyhelminthes
9 The Gnathifera: Rotifers, Acanthocephalans, and two smaller groups
10 The Rotifers and Acanthocephalans
11 The Nemertines
12 The Molluscs
13 The Annelids
14 The Arthropods
15 Two Phyla of Likely Arthropod Relatives: Tardigrada and Onychophora
16 The Nematodes
17 Four Phyla of Likely Nematode Relatives: Nematomorpha, Priapulida, Kinorhyncha, and Loricifera
18 Three Phyla of Uncertain Affiliation: Gastrotricha, Chaetognatha, and Cyliophora
19 The Lophophorates (Phoronids, Brachiopods, Bryozoans) and Entoprocts
20 The Echinoderms
21 The Hemichordates
22 The Xenoturbellids
23 The Nonvertebrate Chordates
24 Invertebrate Reproduction and DevelopmentโAn Overview