. Elementary text-book of zoology. Zoology. FIG. 10.—Zoospores of AetliaUum sept it-it M :ifier de Bary. a, in condition of hatching; b, as mastigopods ; c, in the amoeboid stage; d, a piece of plasmodium. lower animals, there is present an undifferentiated albuminous substance known as sarcode, the contractile matrix of the body. The viscous contents of vegetable cells, known as protoplasm, possesses likewise the power of contractility, and re- sembles sarcode in its most essential properties. Both present the same chemical reactions and agree in the fre- quent presence of cilia, vacuoles, an
. Elementary text-book of zoology. Zoology. FIG. 10.—Zoospores of AetliaUum sept it-it M :ifier de Bary. a, in condition of hatching; b, as mastigopods ; c, in the amoeboid stage; d, a piece of plasmodium. lower animals, there is present an undifferentiated albuminous substance known as sarcode, the contractile matrix of the body. The viscous contents of vegetable cells, known as protoplasm, possesses likewise the power of contractility, and re- sembles sarcode in its most essential properties. Both present the same chemical reactions and agree in the fre- quent presence of cilia, vacuoles, and streams of granules. Pulsating spaces, the contractile vacuoles, are not ex- clusively a possession of sarcode, but may also occur in the protoplasm of vegetable cells (Gonium, Chlamydo- monas, Chcetopkora). The contractility of the protoplasm of vegetable cells is, as a rule, limited by the cellulose membrane, but in the naked cells of Volvocina and Saprolegnia, and in the amoeba-like forms occurring in the development of Myxomycetes, the contractile power is as intense as in the sarcode of Infusoria and Rhizopoda. The amoeboid move- ments of the plasmodium of Myxomycetes (fig. 10) are not inferior in intensity to those of a genuine Amoeba belonging to the Rhizo- poda, , Amceba polypodia (prin- ceps], (fig. 11). In these similar phenomena of movement of the lower animals and plants we seek in vain for any test of volition, the interpretation of which will depend upon the individual judgment of the observer. The faculty of sensation, which is inconceivable as a function of matter and which must be always FIG. 11.—Amoeba Dtiftyiofpjicera polypodia. pre-supposed wherever we have to do with voluntary movement, can by no means be affirmed with certainty in all animal organisms. Many of the lower animals entirely lack a nervous system and sense organs, and, on stimulation, exhibit *<\ *. '• '• • ".' \\ //// w- //vx ,.V;ilil^^. X, nucleus. Pr, contractile vacu
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
