Originally published in 1939, this book details how animals living in water regulate their internal water content.

Preface; Introduction and definitions; 1. Protozoa; 2. Coelenterata; 3. Echinoderma; 4. Scolecida; 5. Annelida; 6. Mollusca; 7. Crustacea; 8. Arachnomorpha; 9. Insecta; 10. Cyclostomata; 11. Elasmobranchii; 12. Teleostomi; 13. Amphibia; 14. Reptilia, aves, mammalia; 15. Osmotic conditions in eggs and embryos; 16. Comments, conclusions and suggestions; Appendix. Notes on methods; List of references; List of Latin generic names; General index.