IO6 HARRIET L. ROBBINS AND C. M. CHILD. 



was used. After weighing, the worms were returned at once to 

 water and then transferred to pyrex tubes fused at one end and 

 of the same diameter as the standard tubes. After washing 

 twice in aqueous indicator solution of the same concentration 

 as that in the standard tubes, each tube was filled with indicator 

 solution to a 3-c.c. level previously marked. The tubes were 

 then sealed without air bubbles by running in on the surface of 

 the fluid about i c.c. of soft paraffin at a temperature just above 

 melting point, the worms being kept at the bottom of the tube 

 to avoid injury from change of temperature. Since leakage 

 past the paraffin plug is difficult to avoid when changes of tem- 

 perature occur and since it was found desirable to reduce the 

 temperature slightly as a means of keeping the animals quiet 

 (see below), the following method of providing for changes in 

 volume of the fluid was used. A piece of closely fitting soft 

 rubber tubing, previously coated with soft paraffin was drawn 

 over the open end of the pyrex tube, leaving 2 to 3 cm. of the 

 tubing beyond the end of the glass. Indicator solution was 

 then added to fill both the glass tube above the paraffin plug and 

 the rubber tube, and the latter is then closed by a screw clasp. 

 This procedure makes impossible the entrance of air past the 

 paraffin plug when the temperature is lowered. Instead of air 

 a small amount of the indicator solution above the plug may be 

 drawn below, but this occurs within the first five minutes or 

 less of the experiment, and with the changes of temperature 

 involved the amount of fluid passing the plug is negligible, so 

 far as the results are concerned. The indicator solution between 

 the paraffin plug and the rubber tubing is visible and serves as a 

 control for the color change below the plug. Closure by means 

 of the rubber tubing and clamp alone was found to be unsatisfac- 

 tory because some of the worms creep into the rubber tubing, 

 where they cannot be seen, and it is therefore impossible to 

 determine whether motor activity is going on and whether all 

 are in good condition. Moreover, pieces in the rubber tubing 

 are often overlooked when the lots are removed from the exper- 

 imental tube and the whole lot becomes valueless for further 

 experiment, unless substitution for the lost pieces is made, but 

 this is at best an undesirable procedure. 



