22 



ANIMALS AND PLANTS. 



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, e.g., 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 vacuole (after 

 Fr E. Schultze). 



