INDEX. 



225 



Protonephridia, 139 



Protopterus, 131 



Protoplasm, 71, 74; discovery of, 

 72; diversity of, 74; general 

 properties of, 74; irritability of, 

 77; streaming of granules in, 75; 

 Schultze's theory of, 20, 73 



Protoplasmic products, 78, 85 



Protozoa, 22, 72, 84 



Proteids, the, 74 



Pseudopodia, 145 



Pseudova, 170 



Race, history of the, 37 



Radiata, the, 21; divided into Cce- 

 lentera and Echinoderma by 

 Leuckart, 22 



Ranvier, nodes of, 115 



Rathke, 21 



Ray's conception of species, 23 



Reaumur, 15 



Receptacula seminis, 144 



Red blood-corpuscles, 106; haemo- 

 globin of, 107; of camel, llama, 

 107; of the Cyclostomes, 107 



Refractive bodies in the eye, 



154 



Regions, the six primary of dis- 

 tribution, 213 



Rejuvenescence, 172 



Relations between individuals of 

 different species, 202 



Relationships of animals, 22 



Remak, 21 



Reproduction, 75, 77; combined 

 modes of, 172; distribution of the 

 asexual and sexual modes 174; 

 sexual, 170 



Respiratory apparatus, develop- 

 ment of the, 130; organs, 123 



Respiratory systems of the verte- 

 brates and invertebrates, 130 



Retina, 153 



Rhabdom, 153 



Rhizocephala, 125 



"Right," 163 



Rigor, heat-, 77; cold-, 77 



Rods and cones, 153 



Rosel von Rosenhof, 1516 



Sacculus, 152 



St. Hilaire, Geoffroy, 16, 26 



Salivary gland (acinous) of Orthe- 



zia, 94 



Salivary glands, 127 

 Sarcode, 72 

 Sarcolemma, 112 

 Savigny, 16 

 Scales, formation of 91 



Schleiden, 20; -Schwann cell 

 theory, the, 70 



Schaffer, 15 



Schultze, Max, 21, 73 



Schwann, 20, 70 



Schvvann's sheath, 115 



Sclerotic coat, 155 



Secreta, 88 



Secretory granules, 92 



Segmental organs, 139, 140 



Segmentation, 164 



Selection, artificial, 52; natural, 52; 

 sexual, 59 



Semicircular canals, 152; function 

 of the, 153 



Sensation in the lower animals, 

 148 



Sense organs, 99; nerve-endings 

 in, 99 



Sensory cells, 98; epithelia, 89, 

 98 



Sexual apparatus, the accessory, 

 144; cells, 87, 94, 171; epithelium, 

 94; development, the different 

 forms of, 192; glands, 140; out- 

 lets of, 140; products, outlets for, 

 143; reproduction, 170, 196; con- 

 ditions governing fertility in, 35; 

 general phenomena of, 175; selec- 

 tion, 59 



Shells of mollusks, 90 



Siebold, C. Th. von, 21 



Sight, organs of, 151 



Siphonophore, nutritive polyp of, 

 124 



Skeletal system, the 47 



Skin of petromyzon, 91; of man, 91 



Smell, organs of, 150 



Somatic cells, 171 



Somatopleure, 191 



Species, 23; the change of varieties 

 into, 36; the intercrossing of, 33; 

 Linnaeus' definition of, 24; logi- 

 cal value of the term, 23; the 

 nature of, 23; Ray's conception 

 of, 23; related to each other in 

 unequal degrees, 36; variation 

 within the, 32; "vicarious spe- 

 cies," 51 



Species and varieties, the crossing 

 of, 32; distinction between, 30 



Spermatozoa, 73, 95, 97, 98, 158 



Spinal cord, section of the human, 

 149; the directive, 176 



Spindle-fibres, 82 



Spontaneous generation, 37, 165 



Splanchnopleure, 191 



Sporocysts, 174 



" Sports," 31 



