General principles of zoology . essed thus: plants usuallytake in carbonic acid and breathe out oxygen, while ani-mals breathe in oxygen and give out carbonic acid. Henceit may be concluded that it must be easy to discover differ-ences which generally obtain between plants and animals,for, as a matter of fact, the laity are never in doubt in•deciding to which realm of nature belong the more highlyorganized animals and plants, which are the only onesknown to them. Doubtful Cases.—But the more one studies this ques-tion, the more difficult becomes the solution of it. Theold zoologists indeed for
General principles of zoology . essed thus: plants usuallytake in carbonic acid and breathe out oxygen, while ani-mals breathe in oxygen and give out carbonic acid. Henceit may be concluded that it must be easy to discover differ-ences which generally obtain between plants and animals,for, as a matter of fact, the laity are never in doubt in•deciding to which realm of nature belong the more highlyorganized animals and plants, which are the only onesknown to them. Doubtful Cases.—But the more one studies this ques-tion, the more difficult becomes the solution of it. Theold zoologists indeed formed the conception that there areorganisms which stand on the limits between the animal king-dom and the vegetable, and the Englishman Wotton namedthese directly plant-animals or zoopJiytcs. No\v we know thatWottons plant-animals are true animals with but a super-ficial similarity to plants; but, by means of the micro-scope, we have become acquainted with numerous lowerorganisms, and it is still doubtful in which of the two. 208 GENERAL PRINCIPLES OF ZOOLOGY. realms of nature these belong. As such may be mentioned the myxomycetes and many flagcllata. Distinction on a Physiological Basis.—If one wishes to discover sharp distinctions between animals and plants, he may take into consideration on theone side physiological, on the other mor-phological, characters. Starting from thephysiological point of view, Linnaeus1ascribed to plants only the capacity ofreproduction and nutrition, but to ani-mals the power of motion and sensationin addition to these. However, weknow that vegetable protoplasm, just aswell as animal, is irritable and is capableof movement, as is shown by the active (After Schmarda.) c, ca- , . , , rina -, /, tergum; s, scu- movements of the lower alga, the great sensitiveness of the Mimosa, and otherplants; but further, we know that even many of the morehighly organized animals, crabs (Fig. 109), lose thepower of locomotion and become fixed, and many fix
Size: 1276px × 1957px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
