PROTOPLASMIC MOVEMENT. 371 



themselves. Protoplasm thus possesses, not only contrac- 

 tility and irritability, but also automatism. 



Protoplasm, in accordance with its low stage of orgasisation, 

 unites in itself the three properties which are usually divided 

 between histologically diflPering elements — in the case of ciliary 

 organs between the protoplasm and the cilia, in the case of 

 muscular organs between the ganglia, the nerves, and the 

 muscles themselves. 



With this agrees its remarkably wide distribution in animal 

 and vegetable organisms, its prevalence among the lowest 

 forms of life in both kingdoms, as well as among embryonic or, 

 above all, young cells, and in the same way the absence of a 

 more complicated anatomical structure. 



Sharply defined limits between protoplasmic movements and 

 those of other organic structures cannot be drawn. As ex- 

 hibiting movements transitional between protoplasmic and 

 muscular movement may be instanced the body-substance of 

 numerous Infusoria,^ the tentacles of Acinetse, the superficial 

 sarcode of Sponges,^ embryonic muscle-cells of higher forms, 

 endothelial cells of many, more especially young, blood-capilla- 

 ries,^ &c. Pigment cells, which are contractile under the in- 

 fluence of a nerve impulse, found in the skin of Crustacea, 

 Fishes, Amphibia, and Reptiles, may be also mentioned in this 

 connection.* Transitions from protoplasmic to ciliary move- 

 ment, or more especially in the other direction, have been 

 observed by De Bary and others in the spores of Myxomy- 



* Th. W. Engelmann, " Contractilitat u. Doppelbrechung," ' Arch. f. d. ges. 

 Physiol.,' xi, p. US, 1875. 



^ Lieberkijlin, ' Ueb. Bewegungserschein. d. Zellen,' p. 346, Marburg, 

 1870. 



' Cf. among otliers : S. Strieker, " Unlersuelmngen iiber die Contractilitat 

 der Capillaren," ' Wiener Sitzungsber. d. Math.-naturw.,' CI. ixxiv, p. 313, 

 1877. 



* An account of the fairly extensive literature in this respect is given by 

 G. Seidlitz, 'Beitriige zur Descendenztheorie,' pp. 31 — 36, Leipzig, 1876, and 

 supplemented by Hering, " Ueb. d. Beweg. d. sternform. Pignientzellen, &c.," 

 communicated by von Hoyer, ' Centralbl. f. d. med. Wiss.,' 1869, No. 4, 

 p. 49. 



