24 WM. A. KEPNER AND B. D. REYNOLDS. 



(b) Apparatus and Technique. 



Individuals can easily be isolated for study by placing a Petri 

 dish, containing the organisms, under a low-powered binocular, 

 locating the animal desired, and transferring it by means of a 

 narrow-mouthed pipette to a plain slide containing a large drop of 

 spring (or distilled) water. The amputations were made with 

 fine glass needles, which can readily be drawn in a small hot flame. 

 It is essential to use hard elastic glass for this purpose. 



At first the operations were made under a binocular, and the 

 slide containing the organism was then transferred immediately to 

 a compound microscope for observation, but later operations were 

 made under the compound microscope, using a 32-mm. objective 

 and a No. 10 eyepiece (B. & L.). The latter method is altogether 

 more satisfactory, since it enables the observer to keep sight of 

 the performance from the very beginning, and also avoids any 

 jarring or shifting of the protoplasms, which might take place 

 while transferring the slide. Practically all of the observations 

 were made under the 16-mm. objective and No. 10 eyepiece. 

 Most of the distances given in this paper were estimated either in 

 terms of the diameter of the field or in terms of the diameters of 

 the shells of the individuals concerned. A later and more satis- 

 factory method is to use a camera lucida and trace the outlines of 

 the experimental objects at definite intervals. By this method 

 exact record can be kept of the relative sizes and positions, as well 

 as the paths followed by each body. 



I. Is Reunion of Cell-body and Fragment the Usual 

 Occurrence? 



In order to determine this we performed approximately one 

 hundred experiments, the majority of which gave positive results. 

 The few negative cases observed were apparently due to one of 

 the following causes : (a) Severe injury to cell with consequent 

 failure on its part to extrude pseudopods, (b) separation from 

 fragment by too great a distance, (c) evaporation of water before 

 completion of reaction. These results have been repeatedly con- 

 firmed by graduate students in this laboratory. Since mucus is 

 involved in the organisms' locomotion, it occurred to us that the 



