26O HUBERT B. GOODRICH. 



a pseudopod with sufficient force to slightly indent the ectoplasm, 

 the pseudopod may slowly withdraw. A brownian movement of 

 pigment granules is frequently initiated. Of these cells the yellow 

 chromatophores are most responsive, the red are less responsive 

 and the melanophores are almost completely inert to tactile 

 stimulation. 



All cells studied seem to show less variety of adaptive response 

 than the amoeba. Thus the only reaction that I have observed 

 is contraction either of the whole or a portion of a cell. 



I have previously referred (Goodrich, '22) to the motion of the 

 fan cells as non-amoeboid. The characteristic streaming of 

 protoplasm which we associate with the amoeba is certainly not 

 present. The phenomenon seems more akin to the movement of 

 diatoms. It is, however, not impossible that this gliding motion 

 may be a factor in the locomotion of many unicellular organisms. 

 Schaefer ('20) in his discussion of amoeboid movement has called 

 attention to the importance of a surface film of streaming proto- 

 plasm external to the ectoplasm and wholly distinct from the 

 familiar streaming of the endoplasm. This film can be observed 

 only indirectly as it carries particles that become entangled in it. 

 Schaefer states (page 106) that "the surface film in amcebas is 

 powerful enough to enable them to move by it." In this case it 

 causes a backward motion. It is also probable (see Schaefer, 

 '20, for discussion) that such a surface film is important in the 

 movement of diatoms, Oscillitoria and even of Gregarines. No 

 adequate explanation has been offered for the motion of this 

 surface film. I have not been able to detect the presence of such 

 a moving film in the fans of the cells studied in this paper although 

 cells have been observed in media containing a suspension of 

 carbon granules. Yet the delicacy of the fan is such as to make 

 the test seem inadequate and it is not impossible that such a 

 mechanism may exist. If so we may have some clue to the motion 

 of many cells in development and in regereration. Moreover this 

 mode of motion seems allied to the power of adhesion of cells. The 

 cells here described are attached to the cover glass by means 

 of the fans. Dr. W. H. Lewis ('22) has raised the question as 

 to why tissue cells adhere in an organism. The mechanics of 

 the gliding motion seems to involve this power of adhesion and 

 thus the two problems may be related. 



