In connection with Mr. H. L. Clark, Mr. Conant undertook to investigate the character of the nervous control of the heart beat in decapod crustaceans. They selected the common edible crab, Callinectes hastatus, and made a series of most careful experiments and dissections which resulted in proving the existence of one inhibitory nerve and two accelerator nerves passing to the heart on each side from the thoracic ganglion. They not only demonstrated the physiological reaction of these nerves, but traced out successfully their anatomical course from the ganglion to the pericardial plexus. It seemed hardly probable from an a priori standpoint that in an animal like the crab there should be any necessity for an elaborate nervous mechanism to regulate the beat of the heart, but their experiments placed the matter beyond any doubt, and have since served to call attention to this animal as a promising organism for the study of some of the fundamental problems in the physiology of the heart. As compared with previous work upon the same subject it may be said that their experiments are the most definite and successful that have yet been made. His chief completed work, the Dissertation on The Cubomedusæ, is here printed; and through it the reader who did not know Conant must decide whether he was well fitted, by training and by natural endowments, for advancing knowledge. I myself felt confident that the career on which he had entered would be full of usefulness and honor. I was delighted when he was appointed to the Adam T. Bruce Fellowship, for I had discovered that he was rapidly becoming an inspiring influence among his fellow students in the laboratory, and I had hoped that we might have him among us for many years, and that we might enjoy and profit by the riper fruits of his more mature labors. Immediately after his examination for the degree of Doctor of Philosophy in June, 1897, he set out for Jamaica to continue his studies at the laboratory which this University had established for the summer at Port Antonio, and he there worked for nearly three months on the development, and on the physiology of the sense-organs, of the Cubomedusæ. His notes and specimens are so complete that I hope it will be possible to complete in Baltimore, at an early day, the work which he had expected to carry on this year. After the sudden and alarming death of the director of the expedition, Dr. J. E. Humphrey, Conant took the burden of responsibility upon himself, and while he fully appreciated his own great danger, he devoted himself calmly and methodically to the service of others who, in their afflictions, needed his help, and he fell in the path of duty, where he had always walked, leaving behind him a clear and simple account of all the business of the laboratory and of his scientific work, and of his own affairs, complete to the day before his death.