THE supra-œphageal ganglion of Anodonta is usually regarded as representing both the cerebral and pleural ganglia, and is commonly spoken of as the “cerebropleural.” Prof. Howes mentions in his “Atlas” that Prof. M. Hartog has occasionally observed a ganglionic swelling on one or both of the cerebro-visceral connectives in front of the pericardium, but that he himself has failed to find any such enlargement. In view of the doubt that exists, it seems to be worth recording that yesterday one of my pupils, A. C. Roxburgh, while dissecting an Anodonta in the Charterhouse laboratory, exposed a well-developed ganglion of the usual orange colour, upon the left connective in the exact position mentioned by Prof. Hartog. Microscopical examination removed all doubt as to the nature of the swelling for numerous ganglion-cells were easily recognised in the teased preparation. It is thus probably more correct to term the anterior ganglion “cerebral” rather than cerebro-pleural. Perhaps some of those who are better equipped for research than is possible or advisable for those engaged in elementary laboratories might find it worth while to examine series of sections of the connective at this region. It is possible that the pleural ganglion may in most cases be represented by but a few ganglion cells the presence of which is not discernible to the unaided eye.