1. It has been shown that there is an almost linear inverse relationship between the transmembrane potential of the somatic muscle cells of Ascaris lumbricoides and the bath temperature between 38° and 20° C.
2. It has also been shown that the spike frequency reflects these changes, decreasing at a rate of 0.6 impulse/sec./mV.
3. D-Tubocurarine interferes with the response of these cells to thermal changes between 380 and 20° C. but it is ineffective below 20° C.
4. It is proposed that the presynaptic nerve fibres are responsible for the thermal sensitivity of the muscle cells, since the amount of depolarizing neurohormone spontaneously released at the neuromuscular junctions would depend upon the temperature.