i6 



ZOOLOGY 



protoplasmic mass may rotate within the cell wall, or there 

 may be narrow channels in which the currents move between 

 banks of more stationary material. The latter motion is de- 

 scribed as circulation. (Fig. 3.) 



FIG 



FIG. 3. The circulation of protoplasm (p) in a cell of a stamen-hair of Tradescanlia. In the 

 channels the granules move back and forth to the various parts of the cell. The remainder of the 

 cell is filled with cell-sap ($) which in these cells is colored. 



Questions on the figure. In what respects are the activities of the protoplasm 

 necessarily limited in this cell as compared with the condition in Amoeba;? Why is 

 circulation an appropriate term? 



25. Demonstrations. The teacher should, if possible, demonstrate proto- 

 plasmic motion to the students with a compound microscope of good magnification. 

 The Amoeba will serve to illustrate the naked streaming motion; Paramecium, 

 rotation; the hairs from the stamens of Tradescantia beautifully illustrate circula- 

 tion. (There is a cultivated species which may be kept blooming in greenhouses at 

 all seasons of the year.) Ciliary motion may be shown in several of the large 

 Protozoa, or by living cells scraped from the esophagus of the frog. 



26. Dissimilation. Motion and the other responses which 

 protoplasm makes to stimuli necessarily represent chemical or 

 physical changes, or both, in the protoplasm. It is well known 

 that complex chemical substances, such as are found in proto- 



