158 PAUL S. GALTSOFF. 



* 



ference being only in the velocity and in the duration of the 

 movement. 



The examination of the paths of various cells shows that their 

 movement is not at all directed towards one another or towards 

 the group of cells. No one cell could be found which acts as a 

 center of attraction for other cells. The coalescence occurs only 

 when one moving cell happens to touch another one, and to stick 

 to its outer layer. The path of the archaeocyte is an irregular 

 winding line; a typical case is shown in Fig. I. The movement 

 of this archaeocyte was followed for 168 minutes. The points 

 where coalescence with other cells occurred are indicated by 

 crosses; the arrows show the direction of the movement. Other 

 cells in the same field of view moved very slowly and passed only 

 few microns; the aggregate was formed exclusively through the 

 activity of the archseocyte. 



f 10 If ->0 



ju.- 



FIG. I. The path of the archaeocyte of Microciona; the line representing the 

 movement of the center of the cell. The observation was made with camera lucida, 

 Zeiss obj. E, and eyepiece 6. The outlines were drawn each two minutes. 



This archaeocyte travelled back and forth in different direc- 

 tions, approaching certain cells from w T hich it withdrew. It 

 coalesced first with the small dermal cell d, with the chaonocyte 

 c, and with two archaeocytes a and b all of which happened to 

 lie in its route. 



The velocity of the movement of the archaeocyte is subject to 



