256 HUBERT B. GOODRICH. 



sidiary fans, as in Fig. 4, which are invisible when making camera 

 drawings, doubtless influence the rate of motion. Nevertheless 

 the results seem to indicate that an increase of temperature causes 

 an increase in the velocity of the movement. The average of all 

 (15) observations at room temperature showed a rate of locomo- 

 tion of 6.3 microns per minute. The average of all (10) observa- 

 tions at higher temperatures (in most cases varying) was 7.3 

 microns per minute. The records of greatest speed were 11.5 

 microns and 10 microns per minute and were attained by cells 

 at the higher temperatures. In the latter case the cell was fol- 

 lowed for 39 minutes. The details of these observations are 

 recorded in the tables in the appendix to this paper. 



A second form assumed by these cells was that exhibiting 

 two fans (Figs. 5, 6, 7). These fans were usually at opposite 

 poles and under their influence the cell became greatly attenuated. 

 In such cases a micro-dissection needle could be passed between 

 the coverslip and the body of the cell (Fig. 3), but the fans were 

 found to be firmly attached. The cell was thus freely suspended 

 like a hammock between two supports the fans forming means 

 of attachment and also of extension. Two typical double fanned 

 or bipolar cells are shown in Fig. 5 and 7 which were drawn from 

 stained preparations. In Fig. 6 are shown two cells attached 

 with one fan pulling in a direction not directly opposed to the 

 other. 



Another extraordinary mode of motion was observed in which 

 the contractility of the cell functioned as well as the gliding motion 

 of the fan. The history of such a cell is shown in Fig. 9. The 

 account begins at 2.44 P.M. with the cell at position I and with 

 a fan at either end. Suddenly a release of the fan occurs and the 

 cell contracts and is thrown into position 2. It again elongates, 

 fans are found at either end positions 3, 4, 5 and at 3.01 a 

 second contraction occurs, throwing the cell into position 6. The 

 process is repeated four times positions 6-9, 9-12, 12-13, and 

 13-18. In each case the cell is elongated by the pulling of the op- 

 posed fans. This unusual mode of motion was observed in a 

 culture from a 17-day embryo. This marked contractility of a 

 mesenchyme cell is almost suggestive of the behavior of muscle 

 cells as described by M. R. Lewis ('20) except that these cells 



