Histochemical procedures indicate that in Pisaster ochraceus and Patiria miniata a diastase-labile carbohydrate occurs in small quantities as fine granules in the peritoneum and muscle of the gut, and in the columnar epithelia of the stomach and ducts of the pyloric caecae. A diastase-resistant carbohydrate occurs abundantly in the storage cells of the pyloric caeca, usually as a matrix surrounding large granules of protein. Neutral lipid droplets occur in small quantities in the columnar epithelium of the cardiac stomach and are abundant in the storage cells of the pyloric caeca. 2. In Pisaster the pyloric caeca increase in size from June to December and decrease in size during the spring at the time when the gonads are growing. The inverse size relationship suggests the withdrawal of material from the caeca for use by the gonads. The pyloric caeca of Patiria seem to remain fairly constant in size during the breeding cycle. 3. In both species prolonged starvation during the breeding period results in shrinkage of the pyloric caeca and reduction of the nutrient reserves to levels insufficient to support normal gonadal development. Starvation most markedly reduces the histochemically detectable carbohydrate in the pyloric caeca. Stomach lipid is reduced in both species, and most of the caecal lipid disappears in Patiria. Even after twenty months of starvation Pisaster specimens still showed considerable lipid in the caeca. 4. The connective tissue and mucus from most parts of the gut appeared to contain neutral and weakly acid mucopolysaccharide components or a single compound with both neutral and acid residues. Fine granules found at the apices of cells in certain regions of the stomach contain a more acid mucopolysaccharide. 5. The histochemical results correlate well with earlier biochemical data available for the two species.
