48. CROTALUS 923 
ment, and was regulating his rattle to a considerable extent 
by what he saw, was manifest from the crescendos and dimin- 
uendos corresponding to my alternating periods of move- 
ment and perfect quiet. But there were diminutions, intensi- 
fications and momentary cessations in the rattle beyond the 
Variations in my movements. My impression was that the 
tail vibration tended to be irregularly rythmic independently 
of the stimulus, though my observations were not sufficiently 
full to establish this surmise. 
“The snake was coiled when I first saw him, but the coil 
was not the strike coil. Nor did he change his position as 
long as I watched him. Even the head was moved very 
little, if at all. So far as I could make out, the only part 
of him in motion was the tip of his tail. Thinking that as 
good a test as I could make of my presence as a rattle entic- 
ing stimulus would be to move slowly and quietly away; 
this I did. At about 80 paces from the snake, the trail, 
curving around a steep slope, took me out of sight of his 
position and beyond the sound of his rattle. The sound 
became so faint at this point that I could not decide posi- 
tively whether it actually stopped or continued but inaudibly 
to me. I am quite sure, however, from its evenness, that 
its general intensity of the whir gradually diminished as I 
moved away. Nor could IJ tell certainly whether I was in 
range of his visian the whole time. 
“Why I so unfortunately failed to return a little later 
to see what was going on, and to take other means of testing 
the snake’s behavior, I do not now recall. Probably I imagined 
I had more important duties elsewhere, though now I doubt 
this. The entire time of the observation was something 
more than 20 minutes. 
“At the time of rattlesnake encounter thus narrated, 
I was greatly interested in the different behavior of this 
individual from that of one of the same species I came 
