342 WILLIAM M. GOLDSMITH 



very difP.ciilt to explain how the tension point at c, figure 19, 

 could be relieved. Since the contractions, mentioned as the 

 fourth factor, are direct compressions of the body wall, they 

 would seem to force the end of the fiber through the body mem- 

 brane. Therefore the movement produced by cyclosis would 

 probably be the only factor which would alleviate this tension. 

 When long fibers, as illustrated in figure 20, were completely 

 ingested, the ciliate became very sluggish and discontinued the 

 usual movements until digestion was nearly completed. 



EFFECT OF THE INGESTED 1\L\TERIAL UPON THE SIZE AND 

 GENERAL APPEARANCE OF THE BODY 



Ingested food causes an unusual variety of shapes of the 

 frontonia's body. Cultures taken directly from the brook have 

 been found to contain individuals of almost every imaginable 

 shape. The various shapes, of course, depend upon the variety 

 of food available. After a few weeks' work the experimenter 

 could cause to be produced many desired fantastic figures. 

 For example, it was a very simple matter to produce the char- 

 acteristic 'half-moon' frontonia shown in figure 23. This was 

 done simply by cutting oscillatoria fibers into pieces slightly 

 longer than the linear expanded length of the average frontonia. 

 The imperfect 'half-moon' shown in figure 24 resulted from the 

 ingestion of a longer fiber than was used in the case of the typical 

 'half -moon,' while the bow-and-arrow-like ciliate (fig. 22) is an 

 unusual case in which a shorter piece of blue-green alga lodged 

 perpendicular to the fiber which produced the 'half-moon.' 

 The interesting case shown in figure 25 is simply a 'half-moon' 

 frontonia in which the action of the digestive fluids caused the 

 ends of the fiber to curl. Had the fiber given way in the center, 

 the shape would have been markedly different. Since the food 

 material includes not only hundreds of the smaller and more or 

 less common fresh-water algae and the slowly moving protozoa, 

 but also the limitless variety of foreign matter and debris which 

 one finds in the sediment of a brook or which may be added to 

 a culture, one is not surprised to find almost any imaginable 

 shape. Moreover, the general appearance of the frontonia not 



