38 ACTION OF AUXETICS AND KINETICS 



fairly rapidly, that of bacteria being nearly at a stand- 

 still. Observed day by day, the amcebulae did not 

 increase much in size, as they would on an ordinary 

 medium, but showed a tendency to lengthen out 

 (fig. 14). This increased to such an extent that 

 the amoeba? after twelve days had quite altered 

 their type, becoming very long and slender 

 (fig. 15). 



Unlike the young forms, these long, slender adult 

 amceba3 move slowly, like a snail, a small quantity 

 of clear protoplasm being protruded at one end and 

 the rest of the body gliding after this. Short lateral 

 pseudopodia sometimes appear, and the body 

 occasionally rounds up, but always soon recovers its 

 length. The appearance of a similar type has been 

 described by Gruber in cultures of Amoeba proteus 

 (PI. VII. B), without, however, any mention as to 

 its mode of origin ; and the A. gi'acilis of Penard 

 (PL VII. D) resembles it closely. We were at first 

 inclined to attribute the variation to the asparagin, 

 especially as these forms were particularly abundant 

 in the neighbourhood of two small crystals of that 

 substance which had appeared on the surface of 

 the jelly ; but neither they nor the minute 

 amcebulae appeared when the experiment was 

 repeated several times. Transferred to a plain 

 2-per-cent. agar jelly, these long forms maintain 

 their appearance for about ten days, in gradually 

 decreasing proportion to the ordinary rounded 

 forms which are also present. Placed on a fresh 

 3-per-cent. asparagin jelly, they at once shrivelled 

 up, and most of them were killed; a few, how- 

 ever, survived and finally became encysted. Their 

 cysts, planted on a plain jelly, gave rise to the 



