ii THE ANIMAL KINGDOM. 



We have seen that the term natural history, as applied to plants and animals, is in- 

 exact, having been used in different senses ; a more exact and suitable one is Biology, 

 which is the science which relates to living beings. It is derived from the Greek 

 ^Los, life, and Uyog, discourse. It is divided into Botany, which relates to plants, and 

 Zoology {tfiop, animal; Uyoi, discourse), the science treating of animals. 



The science of zoology may be subdivided thus : 



MoKPHOLOGY, or gross Anatomy, and the anatomy of the tissues 



(Histology), based on embryology. 

 Physiology and Psychology. 

 ZOOLOGY. \ Repeoduction and Embkyology. 



Systematic Zoology, or Classification. 

 Paleontology, the study of fossil animals. 

 Zoo-GEOGBAPHY, or the geographical distribution of animals. 



MOEPHOLOGY. 



Inoeganic and Oeganic Bodies. 



The differences between the inorganic or mineral bodies, and organic or living 

 bodies, are not always appreciable to the untrained eye and mind. Mineral bodies, 

 such as water, and solid minerals such as quartz, salt, or lime, may assume definite 

 crystalline shapes, and such shapes may grow, i. e. increase in size, by the addition, on 

 the outside, of particles of the same substance. Minerals may exist in three different 

 states, gas or vapor, fluid, or solid. The air, carbonic acid gas, and water are min- 

 erals, as much so as lime or salt. Rocks are made up of minerals, and thus the earth, 

 the air, and water are of mineral origin. Minerals may assume plant-like shapes, as 

 seen in the beautiful forms and delicate leaf-like tracery of the frost on our windows. 

 The drops of sea-water dashed by the waves upon one's coat-sleeve may be seen under a 

 glass to evaporate and the solid particles left to arrange themselves in beautiful but 

 definite crystalline forms. By watching the evaporation of salt water under the micro- 

 scope, the crystals may be seen actually to grow, i. e. to build themselves up, to extend 

 and enlarge in size. " If," as Huxley states, " a crystal of common salt is hung by a 

 thread in a saturated solution of salt, which is exposed to the air so as to allow the 

 water to evaporate slowly, the molecules of the salt which is left behind and can no 

 longer be held in solution, deposit themselves on the crystal in regular order and in- 

 crease its size without changing in form. And, in this way, the small crystal may grow 

 to a great size." Thus growth in minerals consists in the addition of particle after 

 particle of solid matter to the outside of the growing body. 



Now, how do living bodies essentially differ from those not living? In the fii-st 

 place, plants and animals are built up of protoplasm. Protoplasm consists of mineral 

 matter, to be sure, but so combined as to form a substance not found in minerals. 

 Moreover, a plant or animal has life ; the plant grows, and, if it is a vine, is capable of 

 some degree of motion, it twines about some post or tree as a support ; the living bird 

 flies, and the living dog runs; after a time the plant or the bird dies, it is then dead. 

 Minerals do not die. Besides, when the plant or animal grows, it increases in size not 

 like minerals, by additions from without, but by manufacturing protoplasm and other 

 organic substances, such as starch and fat, within its body. Thus organisms or living 

 beings grow by additions from within, these additions being produced by the livino- 

 being itself. After a while this process stops and it becomes dead. As Professor Hux- 



