1. The viability of Pandalus borealis at temperatures from ll-5o-20-3o C. has been studied. Thermal death occurs at 11-5o C.
2. When the mean lethal exposure to various temperatures is plotted against temperature two curves are obtained, meeting at a critical temperature of about 16-5o. The temperature coefficients Q10, ft and m have different values above and below this critical temperature. This indicates that the causes of death are different above and below 16-5o C.
3. When animals are transferred suddenly from 5–6o C. to a high temperature (19-2o and 20-3o) they die after a shorter exposure to that temperature than when the change is made gradually over a period of one hour.
4. The rate of scaphognathite beat varies not only with the activity of the animal but also with its previous history; the disturbance due to catching increases the rate enormously, and the effect of this lasts 2–3 days.
5. The rate of scaphognathite beat increases not only with rising temperature, but also with the length of time the animal is exposed to a high temperature; it is suggested that this unusual behaviour may be due to a decline of inhibition of the scaphognathite.