i6 



ZOOLOGY 



veloped by a cell-wall or is naked. If without a wall, it may- 

 send out foot-like projections into which there passes a stream 

 of granules, as in the Amceba (see Fig. 2) ; if enclosed, the 

 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. 3. 



- s 



P — 



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 {s) 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 Amcebaj? Why is 

 circulation an appropriate term? 



25. Demonstrations. — It is very desirable that the student actually see proto- 

 plasmic motion with a compound microscope of good magnification. The Amceba 

 will serve to illustrate the naked streaming motion; Paramecium, rotation; the 

 hairs from the stamens of Tradescanlia beautifully illustrate circulation. (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 Infusoria, as 

 Stentor, Paramecium, or Vorticella, or by living cells on the gills of clams and 

 mussels. 



26. Dissimilation." — Motion and the other responses which 

 protoplasm makes to stimuli necessarily represent chemical or 



