Changes in the neurosecretory cell (cell A and cell B) cytology of Semperula maculata subjected to thermal acclimation (32°c + 0.5°c and 15°c + 0.5°c) for 10 days have been investigated. Of the two temperatures in which slugs are acclimated striking changes were evident in 32°c than 15°c. After acclimation treatment (15°c) there was increase in neurosecretory material and nuclear diameter in cell A and cell B. While on 32°c acclimation, nuclear diameter of the slug showed enlargement and neurosecretory material intensity was lowered in cell A and cell B. The rate of neurosecretory material synthesis was not varied in both that is in cold and warm acclimated cell A and cell B. As nuclear diameter did not showed much more differences in cell A and cell B. But there may be variation in transportation of neurosecretory material in cell A and cell B in warm acclimated and cold acclimated slug as neurosecretory material on cold acclimation accumulated whereas on warm acclimation there may be more transportation. The adaptive significance and neuroendocrine system of Semperula maculata is discussed in relation to temperature acclimation.