G EX ERA L A XA TOM 1 '. 



75 



by pigments taken up by imbibition, in which numerous 



strongly - refracting 



granules 



FIG. 16. Amceba protetts. (After Leidy.) 

 ek, ectosarc ; en, entosarc ; cv, contractile 

 vacuole ; , nucleus ; A', food-vacuoles. 



are embedded. The vital char- 

 acteristics of this substance 

 are movement, irritability, 

 power of assimilation and of 

 reproduction. 



Movement of Proto- 

 plasm. Movement expresses 

 itself firstly in changes of form 

 of the whole body amoeboid 

 movement and secondly in 

 the change of position of the 

 small granules in the interior 

 of the protoplasm stream- 

 ing of granules. Examples of 

 amoeboid movement (Fig. 16) 

 are chiefly the movements of 

 many protozoa, and of the 



colorless blood-cells (white blood-corpuscles) of multicellular 

 animals ; here the protoplasmic body sends out coarser and 

 finer projections, which may be again withdrawn, serving 

 for locomotion and hence called pseudopodia or false feet. 

 The streaming of granules can be observed in the interior 

 of the cell-body, as well as in the pseudopodia extending 

 from this. The pseudopodia may even be so fine as to be 

 at the limits of visibility with our strongest magnifications 

 (Fig. I/), yet in them it can still be observed that the 

 granules wander hither and thither like walkers on a prom- 

 enade, simultaneously centripetally and centrifugally, some 

 with greater, others with less speed. And yet the granules 

 are only passively moved by the protoplasm which is at the 

 basis. For if we feed the creature with some arbitrarily- 

 chosen pigment granules, e.g., finely-pulverized carmine, 

 these pigment granules show the same remarkable stream- 

 ing. Indeed nothing is better suited for illustrating the 

 great complexity in the structure of protoplasm than these 



