THEORIES OF CHEMOTAXIS AND PHAGOCYTOSIS 223 



the surface ahead, and on being released they are thrown out 

 with some force. If a piece of shellac, paraffin, styrax, or 

 Canada balsam be brought in contact with the surface of the 

 drop, however, the drop flows around it immediately, and 

 takes it within its substance, where it is soon dissolved. Even 

 more strikingly like phagocytosis and intracellular digestion, 

 however, is the result of a similar experiment with a piece of 

 glass covered with shellac ; the chloroform " ameba " takes it 

 up as readily as it does the shellac alone, but after all the 

 coating is dissolved away the piece of glass is then cast out of 

 the drop. The resemblance to the engulfing, digestion, and 

 excreting of indigestible particles of bacteria, etc., by amebse, is 

 so striking that it seems impossible that there can be any funda- 

 mental differences in the two processes. It will also be noticed 

 that the drop takes in only what it can dissolve and rejects 

 what it cannot. 



One of the most remarkable actions of the ameba3 which 

 seems almost certainly the result of voluntary action is this : 

 Oftentimes in feeding, an ameba gets hold of a suitable material 

 which is in the form of a long thread, much too long for the 

 ameba to surround. It then proceeds to coil up the thread 

 within its body, by stretching a slight distance along the 

 thread, bending over, and forming a bend in the thread, and 

 by repeating the process it crowds the thread into a neat coil 

 within its body, where it can be digested. The process is done 

 so systematically and with such evident adoption of the means 

 at hand to the desired end, that it seems as if it must be an 

 adaptation of the ameba to circumstances, the result of long 

 experience or of heredity. That an artificial ameba can per- 

 form the same maneuvers seems hardly credible, but it is readily 

 done with almost no difference in detail. If the chloroform 

 drop is given a long fine thread of shellac, it proceeds to bend 

 the thread in the middle, and to send pseudopodia out along 

 the thread to pull it into the drop, coiling it up inside as the 

 chloroform softens the substance of the thread, until it is all 

 contained within the drop, provided, of course, that it is not too 

 long (a thread six times as long as the chloroform drop may be 

 taken in completely). The bending and coiling of the thread 

 in this experiment is entirely in accord with the known laws 

 and phenomena of surface tension. 



Fully as striking an ameboid action as the coiling up of a 

 thread too long to be taken in, is the building, by some of the 

 protozoa closely related to the ameba (Difflugid) of a shell 

 which the animal seems to form by cementing together grains 



