FIG.

77. A polyp, (Tubularia indivisa ;) m, mouth; o, ovaries; p, tentacles 78. Blood disks in man, magnified.

82. Portion of a vein opened, to show the valves,

83. Network of capillary vessels.

84. Dorsal vessel of an insect, with its valves.

85. Cavities of the heart of mammals and birds.

88. Heart and bloodvessels of a gasteropod mollusk, (Natica.) 89. Tracheæ, or air tubes of an insect; s, stigmata; t, trachea. 90. Relative position of the heart and lungs in man.

91. Respiratory organs of a naked mollusk, (Polycera illuminata.) 92. Respiratory organs (gills) of a fish.

93. Vesicles and canals of the salivary glands.

94. Section of the skin, magnified, to show the sweat glands; a, the cut:s; b, blood-layer; c,epidermis; g, gland imbedded in the fat-layer,(f.)

95. Egg of a skate-fish, (Myliobatis.)

96. Egg of hydra.

97. Egg of snow-flea, (Podurella.)

98. Section of an ovarian egg; d, germinative dot; g, germinative vesicle; s, shell membrane; v, vitelline membrane.

99. Egg cases of Pyrula.

100. Monoculus bearing its eggs, a a.

101. Section of a bird's egg; a, albumen; c, chalaza; e, embryo; s, shell; y, yolk.

102. Cell-layer of the germ.

103. Separation of the cell-layer into three layers; s, serous or nervous layer; m, mucous or vegetative layer; v, vascular or blood layer.

104. Embryo of a crab, showing its incipient rings.

105. Embryo of a vertebrate, showing the dorsal furrow.

106-8. Sections of the embryo, showing the formation of the dorsal canal. 109. Section, showing the position of the embryo of a vertebrate, in re

lation to the yolk.

110. Section, showing the same in an articulate, (Podurella.)

111-22. Sections, showing the successive stages of development of the embryo of the white-fish, magnified.

123. Young white-fish just escaped from the egg, with the yolk not yet fully taken in.

124, 125. Sections of the embryo of a bird, showing the formation of the allantois; e, embryo; xx, membrane rising to form the amnios; a, allantois; y, yolk.

126. The same more fully developed. The allantois (a) is further de

FIG.

veloped, and bent upwards. The upper part of the yolk (d d) is nearly separated from the yolk sphere, and is to become the intestine. The heart (h) is already distinct, and connected by threads with the blood-layer of the body.

127. Section of the egg of a mammal; v, the thick vitelline membrane, or chorion; y, yolk; s, germinative dot; g, germinative vesicle. 128. The same, showing the empty space (k) between the vitelline sphere and chorion.

129. Shows the first indications of the germ already divided in two layers, the serous layer, (s,) and the mucous layer, (m.)

130. The mucous layer (m) expands over nearly half of the yolk, and becomes covered with many little fringes.

131. The embryo (e) is seen surrounded by the amnios, (b,) and covered by a large allantois, (a;) pe, fringes of the chorion; p m, fringes of the matrix.

132. Hydra, showing its reproduction by buds.

133. Vorticella, showing its reproduction by division.

134. Polyps, showing the same.

135. A chain of Salpæ.

136. An individual salpa; m, the mouth; a, embryos.

137. Cercaria, or early form of the Distoma.

138. Distoma, with its two suckers.

139. Nurse of the Cercaria.

140. The same, magnified, showing the included young.

141. Grand nurses of the Cercaria, enclosing the young nurses.

142. Stages of development of a jelly-fish, (Medusa ;) a, the embryo in its first stage, much magnified; b, summit, showing the mouth;

c, f, g, tentacles shooting forth; e, embryo adhering, and forming a pedicle; h, i, separation into segments; d, a segment become free; k, form of the adult.

143. Portion of a plant-like polyp, (Campanularia) a, the cup which bears tentacles; b, the female cup, containing eggs; c, the cups in which the young are nursed, and from which they issue. 144. Young of the same, with its ciliated margin, magnified. 145. Eye of the perch, containing parasitic worms, (Distoma.) 146. One of the worms magnified.

147. Transformations of the canker-worm, (Geometra vernalis ;) a, the canker worm; b, its chrysalis; c, female moth; d, male moth. 148. Metamorphoses of the duck-barnacle, (Anatifa ;) a, eggs, magnified; b, the animal as it escapes from the egg; c, the stem and eye appearing, and the shell enclosing them; d, animal removed from the shell, and further magnified; e, f, the mature barnacle, affixed. 14 Metamorphoses of a star-fish, (Echinaster sanguinolentus,) showing the changes of the yolk, (e;) the formation of the pedicle, (r;) and the gradual change into the pentagonal and rayed form.

FIG.

150. Comatula, a West India species, in its early stage, with its stem 151. The same detached, and swimming free.

152. Longitudinal section of the sturgeon, to show its cartilaginous vertebral column.

153. Amphioxus, natural size, showing its imperfect organization. 154. Section of the earth's crust, to show the relative positions of the rocks composing it; E, plutonic or massive rocks; M, metamorphic rocks; T, trap rocks; L, lava. 1. Lower Silurian formation; 2. Upper Silurian; 3. Devonian; 4. Carboniferous; 5. Trias, or Saliferous; 6. Oolitic; 7. Cretaceous; 8. Lower Tertiary or Eocene; 9. Upper Tertiary, or Miocene, and Pleiocene; 10. Drift.

155. Fossils of the Palæozoic age; a, Lingula prima; b, Leptæna alternata; c, Euomphalus hemisphericus; d, Trocholites ammonius; e, Avicula decussata; f, Bucania expansa; g, Orthoceras fusiforme; i, Cyathocrinus ornatissimus, Hall; j, Cariocrinus ornatus, Say; k, Melocrinus amphora, Goldf.; 1, Columnaria alveolata; m, Cyathophyllum quadrigeminum, Goldf.; n, o, Caninia flexuosa; p, Chætetes lycoperdon.

156. Articulata of the Paleozoic age; a, Harpes; b, Arges; c, Brontes ; d, Platynotus; e, Eurypterus remipes.

157. Fishes of the Paleozoic age; a, Pterichthys; b, Coccosteus; c, Dipterus; d, palatal bone of a shark; e, spine of a shark.

158. Representations of the tracks of supposed birds and reptiles in the sandstone rocks.

159. Supposed outlines of Ichthyosaurus, (a,) and Plesiosaurus, (b.) 160. Supposed outline of Pterodactyle.

161. Shells of the Secondary age; a, Terebratula; b, Goniomya; c, Trigonia; d, Ammonite.

162. Supposed outline of the cuttle-fish, (a,) furnishing the Belemnite. 163. Radiata from the Secondary age; a, Lobophyllia flabellum; b, Lithodendron pseudostylina; c, Pentacrinus briareus; d, Pterocoma pinnata; e, Cidaris; f, Dysaster; g, Nucleolites.

164. Shells of the Cretaceous formation; a, Ammonites; b, Crioceras; c, Scaphites; d, Ancyloceras; e, Hamites; f, Baculites; g, Turrilites.

165. Shells of the Cretaceous formation; a, Magas; b, Inoceramus; c, Hippurites; d, Spondylus; e, Pleurotomaria.

166. Radiata from the Cretaceous formation; a, Diploctenium cordatum; b, Marsupites; d, Galerites; c, Salenia; e, Micraster cor anguinum.

167 Nummulite.

168. upposed outline of Paleotherium.

169. Supposed outline of Anoplotherium.

170 Skeleton of the Mastodon, in the cabinet of Dr. J. C. Warren.

INTRODUCTION.

EVERY art and science has a language of technical terms peculiar to itself. With those terms every student must make himself familiarly acquainted at the outset; and, first of all, he will desire to know the names of the objects about which he is to be engaged.

The names of objects in Natural History are double; that is to say, they are composed of two terms. Thus, we speak of the white-bear, the black-bear, the hen-hawk, the sparrowhawk; or, in strictly scientific terms, we have Felis leo, the lion, Felis tigris, the tiger, Felis catus, the cat, Canis lupus, the wolf, Canis vulpes, the fox, Canis familiaris, the dog, &c. They are always in the Latin form, and consequently the adjective name is placed last. The first is called the generic name; the second is called the trivial, or specific

name.

These two terms are inseparably associated in every object of which we treat. It is very important, therefore, to have a clear idea of what is meant by the terms genus and species; and although the most common of all others, they are not the easiest to be clearly understood. The Genus is

founded upon some of the minor peculiarities of anat、mica. structure, such as the number, disposition, or proportions of the teeth, claws, fins, &c., and usually includes several kinds. Thus, the lion, tiger, leopard, cat, &c., agree in the structure of their feet, claws, and teeth, and they belong to the genus Felis; while the dog, fox, jackal, wolf, &c., have another and a different peculiarity of the feet, claws, and teeth, and are arranged in the genus Canis.

The Species is founded upon less important distinctions, such as color, size, proportions, sculpture, &c. Thus we have different kinds, or species, of duck, different species of squirrel, different species of monkey, &c., varying from. each other in some trivial circumstance, while those of each group agree in all their general structure. The specific name is the lowest term to which we descend, if we except certain peculiarities, generally induced by some modification. of native habits, such as are seen in domestic animals. These are called varieties, and seldom endure beyond the causes which occasion them.

Several genera which have certain traits in common are combined to form a family. Thus, the alewives, herrings, shad, &c., form a family called Clupeidae; the crows, blackbirds, jays, &c., form the family Corvidæ. Families are combined to form orders, and orders form classes, and finally, classes are combined to form the four primary divisions, or departments, of the Animal Kingdom.

For each of these groups, whether larger or smaller, we involuntarily picture in our minds an image, made up of the traits which characterize the group. This ideal image is called a TYPE, a term which there will be frequent occasion to employ in our general remarks on the Animal Kingdom. This image may correspond to some one member of the group; but it is rare that any one species embodies all our 'deas of the class, family, or genus to which it belongs.