During a visit to Minorca, in 1858, he noticed an "ignorant fisherman" marking his clothes with the "purple of the ancients." This event led to the publication of the scholarly Memoire sur la Pourpre (1859), in which, by the citation of classical authorities and in other ways, he established the fact that the purple was probably that which is produced in certain species of Murex and Purpura, by what is now known as the hypobranchial gland ; and showed that the secretion of the gland acquires its final colour by exposure to the sunlight. A summary of this work appeared in vol. x. of the Proceedings of this Society.