ABSTRACT
This work was undertaken at the suggestion of Professor W. K. Brooks for the purpose of getting, if possible, some further hint upon the significance of the larval form in Echinoderm phylogeny. It was carried on from October, 1889, to April, 1891; from June to October, 1890, at the Laboratory of the United States Fish Commission at Wood’s Hall, Massachusetts, where the living animals were studied, and for the remainder of the time in the Biological Laboratory of the Johns Hopkins University, where the work was upon the preserved material. My heartiest acknowledgments are due to Professor Marshall McDonald, U.S. Fish Commissioner, for the advantages furnished at the Government Laboratory; and to Professor Brooks, of this university, who has so kindly placed at my service the preserved material, the preparations, and drawings, which formed the basis of his recent paper before the National Academy (4).
