viii CONTENTS 



CHAPTER XXX.— ANIMAL DEFENCES— RETREAT 



Page 

 Mammals (Mammalia) — Monkeys and Baboons, Chamois, Antelopes, Rumination 

 as facilitating Retreat, Importance of Dwellings and Refuges with reference 

 to Retreat, Signalling Coloration - - - 3^3 



Birds (Aves) — African Ostrich, Rails, Extinction of Dodo, Flight as a means of 



Retreat, Woodpeckers, Diving Birds 367 



Reptiles (Reptilia) — Brittle Tails of Lizards, Importance of Cylindrical Shape in 



Snakes, &c. - 370 



Amphibians (Amphibia)— Wrestler Frog -------- 371 



Invertebrates- Ink of Cuttle-Fishes, Detachable Foot-Region of some Land- 

 Snails, Springing Molluscs, Ants and Bombardier Beetles, Use of Suspensory 

 Threads (Spiders, Caterpillars, Slugs), Crustaceans, Sacrifice of Part of Body 

 in Annelids, Possible Origin of Segmentation ------- 372 



ANIMAL RESPIRATION— THE BREATH OF LIFE 



CHAPTER XXXI.— ANIMAL RESPIRATION — GENERAL PRIN- 

 CIPLES—BREATHERS IN WATER AND BREATHERS IN AIR 



General Principles — Nature of and Necessity for Breathing or Respiration, 



Breathing by General Surface, Special Breathing Organs - - - - 376 



Breathers in Water and Breathers in Air — Process essentially the same 



in all cases, Relation between Plants and Animals as regards Breathing - - 378 

 « 

 CHAPTER XXXIL— ANIMAL RESPIRATION— VERTEBRATES 

 THAT BREATHE IN WATER 



Nature and Development of Gill-Clefts, Their possible origin in remote ancestral 



forms - - - - - - - - - - - - - -381 



Fishes (Pisces) as Breathers in Water — Nature of Gills, Lampreys and Hags 

 (Cyclostomata), Sharks and Rays (Elasmobranchii), Sea-Cats (Holocephali), 

 Ordinary Bony Fishes (Teleostei) - 383 



Primitive Vertebrates (Protochordata) — Lancelet, Ascidians or Tunicates, 



Acorn-headed Worms ------ 388 



CHAPTER XXXIIL— ANIMAL RESPIRATION— NEMERTINES— 

 MOLLUSCS WHICH BREATHE IN WATER 



Nemertine Worms (Nemertea)— Some resemblance to Vertebrates - - - 391 



Molluscs (MoUusca) — Mail-Shells, &c. (Protomollusca) ; Head-Footed Molluscs 

 (Cephalopoda)— Cuttle-Fish, Pearly Nautilus; Snails and Slugs (Gastropoda) — 

 Ormer, Keyhole Limpet, Whelk and Purple Shell, Common Limpet, John 

 Knox's Limpet, Sea-Hare, Sea-Lemon, &c. ; Bivalve Molluscs (Lamellibranchia) 

 — Mussels, Cockles, Oysters, &c. -------., 3gj 



CHAPTER XXXIV.— ANIMAL RESPIRATION— JOINTED-LIMBED 

 ANIMALS WHICH BREATHE IN WATER 



Crustaceans (Crustacea) — Common Lobster, Freshwater Crayfish, Common 

 Prawn, Hermit-Crabs, Crabs, Mantis-Shrimps, Sand- Hoppers, Skeleton- 



