equipment, 1 5 ; perception of 

 light, 21 ; susceptibility to vibra- 

 tions, 71 ; reaction to stimuli, 

 126-7; eye-spots of, 156 

 See also Amoeba 

 Pumphrey, Professor, 171, 173 



Rabbits, 85 



Racoons, their sense of touch, 1 20 



Radar, 183, 187 



Rats : eyesight, 28 ; hearing, 75 ; 



experiments in intelligence of, 



96 ; sense of taste, 1 1 2 

 Rattlesnakes : sense of touch, 115; 



ability to detect infra-red 



radiation 

 Rays : hearing, 1 74, 177; sensory 



pits in, 181, 215; electric organs 



of, 193 



Receptor cells: for smell, 196-7; 

 in taste-bulbs, 204; for touch, 

 211-13; for temperature and 

 pain, 213-14; gravity receptor, 

 2 1 9-20 ; angular-acceleration- 

 receptor, 219-20 



Redshanks, alarm note of, 74 



Reptiles : variations of sense per- 

 ception, 17-18; sight: varia- 

 tions in role of the eye, 24-5 ; 

 eye-coverings, 25, 139; optical 

 mechanism, 46-7, 147; field 

 observations and experiments, 

 47-54; colour vision, 47-8, 52, 

 154; hearing: variations in, 

 72 ; observations and experi- 

 ments on, 78-80 ; structure of the 

 ear, 177; smell: the tongue a 

 detector of smells, 91 ; olfactory 

 mechanism, 199-200; touch: 

 experiment to test response, 119 



Retrievers, their scenting powers, 

 105 



Rhinoceros, its short-sightedness, 

 65, 67 



Ringed plover, 135 



Roach 1 9 1 



Robins their hearing, 73 



Rodents, their hearing, 74-5 



Roe Deer, their excretion of scent 

 from glands, 107 



Rotifers : their limited sensory 

 equipment, 15-16; suscepti- 

 bility to vibrations, 71 



INDEX 237 



Salamanders : field observations 

 and experiments on their sight, 

 43, 46 ; sense of smell, 200 

 Sand Lizards : colour vision, 47, 

 52 ; acuity of sight, 49 ; field 

 observations on their sight, 51 ; 

 hearing, 73 ; field observations 

 and experiments on their hear- 

 ing, 78-80 

 Savage, Dr. Maxwell, 91 

 Scallop, eye-spots of, 1 59-60 

 Scarab beetles, their sense of 



smell, 202 

 Sea anemones : responsive to touch, 

 119; few special sense-organs, 

 127-8; co-ordination of their 

 cells, 128; nerve-cells, 128, 131, 

 133; reaction to chemical sti- 

 muli, and to light, 129-30 

 Sea-cows, their sense of smell, 198 

 Sea snail {Bullia), its sense of 



smell, 207 

 Sea-squirts. See Ascidians 

 Seals : good sight on land and in 

 water, 29 ; lack naso-lachrymal 

 ducts, 139; optical mechanism, 

 153; use of sonar, 190; sense of 

 smell, 198; their whiskers as 

 tactile organs, 209; their fast 

 before breeding, 224 

 Sensations : additional to sense of 

 touch, 114; in cold-blooded 

 animals, 1 15 

 Sensilla, of insects, 180, 201 

 Sensory cells, function of, 13 1-3 

 Sensory pits, in sharks and rays, 



2'5 . . . . 



Shape, birds' instinctive recogni- 

 tion of, 56-8 

 Sharks: scenting power, 91, 99- 



100; hearing, 174, 177, 191-2; 



sense organ similar to lateral 



line, 181 

 Shearwaters, homing ability of, 



226 

 Sheep, 85 

 Shield bugs, 99 

 Short-eared Owl : its sight, and 



field observations on, 60-1 

 Short neck theory, 56-8 

 Shrews : experiments on their 



sight, 67-8 ; sense of touch, 1 20 



