CONTENTS 



CHAPTER PAGE 



VI. — Sponges (Porifera) . . . . .104 



Form and habits — Habitat and seasons — 



Associates — A winter study of living 

 sponges. 



VIL— The Hydras, Fresh Water Jellyfishes 



{Coslenterata) . . . • • .112 



Form and habits — Habitat — Food — Associates 

 — Collecting and aquarium study — Common 

 kinds. 



VIII. — Free-Living Flatworms (Planaria) . .119 

 Planarians and their habits — Habitat — Aqua- 

 rium study — Common forms. 



IX. — Wheel Animalcules {Rotifera) . .127 



Rotifer structures — Habits — Resistance to 

 cold and drought— Typical forms. 



X. — Bryozoans (Bryozoa or Polyzoa) . . . 131 



Form and habits — Collecting — Common 

 forms. 



XI. — Threadworms (Nematoda) and Bristle- 

 worms ipiigochceta) . . . -139 

 Threadworms — Hair snakes — Bristle worms — 

 Habits and food. 



XII. — Leeches (Hirudinea) . . . . .148 

 Form and habits — Leech bites — Food — Col- 

 lecting — Common forms. 



XIII. — Crustaceans (Crustacea) . . . -158 

 Form and habits of crustaceans in general — 

 Classification— General description — The 

 smaller crustaceans, fairy shrimps, water- 

 fieas, copepods, ostracods — The larger crus- 

 taceans, scuds, isopods, crayfishes. 



XIV. — Water-Mites (Hydracarina) . . .175 

 Form and kinship to spiders — Habits and 

 habitat — Common forms. 



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