3171. Nervous system. 25 Color Photomicrographs. 1. Paramaecium neuromotor system 2. Ventral nerve cord of earthworm, t.s. 3. Brain of insect, frontal section. 4. Giant nerve fibres of Sepia 5. Brain of frog, t.s. 6. Motor nerve cell 7. Nerve cells, t.s.