JENKINS AND Cartson, Nervous Lmpulse in Worms. 263 
imal electrodes to the nerve cord near the reacting musculature 
than when applied by the distal electrodes some centimeters 
away from the reacting portion. The incessant relaxation and 
contraction caused, no doubt, in part by the injury in the 
dissection and by the pull of the lever, are almost entirely ab- 
sent in forms like Bispira and Cirratulus; they are quite pro- 
nounced in Glycera and Lumbriconereis and even more so in 
Aulastomum, while in Lumbricus they present difficulties 
which we have thus far been unable to surmount. The unequal 
relaxation of the musculature at the moment of stimulation 
caused variations in the height of contraction, which, together 
with the unequal efficiency of the distal and proximal stimuli, 
rendered comparison of the tracings very difficult, as little 
guidance could be had in the height of contraction. We found, 
however, that in many instances the height of contraction varied 
50% without any appreciable variation of the latent time. But 
the latent time seemed to vary with the strength of the stimu- 
lus, and stronger stimuli were always used for the stimulation 
by the distal electrodes to secure approximately the same 
height of contraction as on proximal stimulation. The elec- 
trodes nearest the reacting musculature were always placed one 
to four centimeters from it and additional precautions were taken 
to insure against direct stimulation of the muscle by escape cur- 
rents. 
The measurements are tabulated in summaries for each 
species, but to give an idea of the make-up of these summaries 
the standard deviation and the coefficient of variability of indi- 
vidual measurements of one typical experiment are given. The 
figures present a representative pair of records from each 
species. The relaxation phase of the myograms is much pro- 
longed and in many cases very irregular, but as this does not 
directly concern the present work only the part of the tracings 
showing the latent time and the height of contraction is given. 
Most of the experiments on the marine forms were carried 
out during the summer of Ig01 and 1902, but some records 
were also obtained during the winter seasons. In the winter 
the temperature of the aquarium varied from 11°C. to 20°C., 
