168 Charles W. Hargitt 
REACTIONS OF NAKED WORMS 
Both tactile and photic tests were made upon specimens which 
had been removed from the tubes, with a view to determine some- 
thing of the character of the responses under such radically changed 
conditions, and also to ascertain the relative sensitiveness of va- 
rious regions of the body. ‘The earlier experiments had sufficed 
to determine that the photic sense was limited to the gill regions. 
It remained, however, to determine whether there was any similar 
limits as to tactile sensibility. ‘This was attempted by gently 
touching the body with the blunt end of a delicate rod.. As might 
have been anticipated, it was found that the gills were by far the 
most highly sensitive. Next to this the immediate region of the 
head was more or less responsive. The mantle-like portion was 
found to be but slightly sensitive to touch, and the posterior, free 
margin of this organ was slightly if at all sensitive to any ordinary 
tactile stimulation. ‘This was likewise the case with almost the 
entire posterior portion of the body, only the prick of a needle or 
the pinch of a forceps inducing some slight muscular reaction. 
Touching the gills always aroused a prompt and vigorous reac- 
tion. If stimuli were applied rapidly, at five to ten seconds inter- 
vals for a few minutes the specimens evidently became fatigued, 
and soon failed to respond, or did so but feebly, the body having 
gone into a condition of muscular contraction resembling tetanus. 
This was followed by apparent efforts on the part of the specimen 
to relax, the gills expanding in spite of continued tactile agitation. 
This condition may have been due to something like a convulsion 
resulting from overstimulation, and perhaps induced in some 
measure by the unusual condition of nakedness. After a rest of 
from five to ten minutes the specimen would again respond in 
exactly the same way, but became sooner unresponsive, lapsing 
into the same condition of fatigue as before. 
Reactions to the shadow stimulus were more or less peculiar 
and uncertain. This was doubtless due in part to the almost — 
constant writhing and twisting of the body under these conditions 
involving what I have previously termed “mixed stimuli” (pp. 
303, 316). ‘The very unusual conditions of nakedness and help- 
