1. The lining epithelium and subjacent tissues of the gut of nudibranch molluscs contain characteristic wandering cells.
2. Although probably amoeboid when alive, the wandering cells after fixation are seen to possess a very definite rounded form. They have a distinct nucleus. The cytoplasm contains a variety of inclusions, and, characteristically, a well-marked eosinophile area.
3. The reaction of the cells to stains is described.
4. The wandering cells were found to take up iron saccharate, which had been injected into the haemocoele.
5. The wandering cells are regarded as a special type of blood cell.
6. Evidence indicates that the wandering cells of nudibranchs are excretory, taking up effete matter from the haemocoele and discharging it into the lumen of the gut.