188 



The normal habit of the worm involves a crawling about over 

 the surface of the rock, to which they cling- tenaciously, often making 

 it difficult to pick them off with a needle; and a stream of water 

 must have at least a moderate velocity in order to wash them off. 

 They normally bore into the sludge, and are also often found in the 

 pores of the rock, from which it is quite difficult to extract them. 



BEHAVIOR WITH REFERENCE TO DRY AND MOIST SURFACES 



A series of experiments was carried on in the laboratory, in 

 diffuse sunlight and at a temperature of about 75 degrees F., in order 

 to determine the behavior of the worms with reference to dry and 

 moist surfaces. 



Bxperiment i. — A drop-culture slide with concave center and 

 ground-glass top surface was used and the concavity filled with tap 

 water. By means of a large needle a straight continuous trail of 

 water was drawn from the concavity very near to the end of the 

 slide. Worms were then placed at the end of the water trail with 

 the following results : — 



1. Slight random movements of the anterior half of the body, 

 which, however, showed the following constant characteristics: (a) 

 refusal to move on to the dry surface; (&) refusal to move off the end 

 of the slide; (c) an apparent recognition of the edge of the water 

 resulting in immediate withdrawal from it; (rf) exploring move- 

 ments at the end of the water trail limited to a small area. 



2. The worms ultimately found the water trail, and almost in- 

 variably followed it uninterruptedly and rapidly to the central cell. 



'Experiment 2. — This experiment differed from the first only in 

 the fact that the water trail was made very tortuous, and the behavior 

 of the worms was identical with that in experiment i. 



Bxperiuicnt 5. — In this experiment a long straight water trail was 

 drawn on the surface of a ground-glass slide, without a central cell, and 

 worms were placed at one end of the trail. Aside from occasional 

 stops accompanied by exploring movements the worms followed the 

 trail to the opposite end, retraced the course, and often repeated this 

 performance for a considerable length of time. 



RELATION TO TEMPERATURE 



The abundance of material made it possible to carry on a long 

 series of experiments, involving a large number of individuals, with 

 the view of determining the temperature limits of life and the effect of 

 different temperatures on the general activities of Lnnibricillus rutilus. 



