The lessons began with general instruction in the use of the microscope, the structure of cells and their union and differentiation into tissues, and then a study of simplest organisms--_Protozoa_. The work was continued through _Porifera_, _Hydrozoa_, and _Actinozoa_, and the types of fossils compared with their living representatives. The periods of occurrence of fossilized remains in the rocks were noted, and the characteristics of the different periods mentioned, but details of stratigraphic character were subordinated to the tracing out of the relations of the animals and the laws which governed the evolution of their forms. Special attention was given to those classes whose history is most complete and which furnish the best specimens for examination. _Echinodermata_, represented by a large number of both living and fossil forms, was made the subject of study the second winter. The common starfish was examined in detail, and with it were compared other members of its class--_Asteroidea_, living and fossil forms in _Ophiuridea_ and _Echinoidea_, the modern _Holothuroidea_, the ancient _Blastoids_ and _Cystoids_, and both extinct and modern _Crinoids_, the last of which were illustrated by alcohol specimens of _Comatula_. Professor Hyatt was assisted in giving these lessons by Miss J. M. Arms, who, in conjunction with him, had previously written the largest of the Science Guides--entitled Insecta--and by Dr. Robert T. Jackson, who has done much work on this group of fossils. One member of the class a few years ago, after receiving these lessons, looked over and prepared a large number of fossils, principally _Crinoids_, belonging to the Natural History Society, and discovered a form of paleozoic _Echinoderm_, which proved to be an interesting new species and was described by Dr. Jackson as _Lepidesthes Wortheni_. The third year of this series consisted of lessons on _Brachiopoda_ exclusively. Professor Hyatt was at that time in correspondence with Dr. C. E. Beecher, of Yale, the distinguished paleontologist, who has made remarkable discoveries and was then investigating _Brachiopoda_, and communications from him regarding this group were from time to time read to the class. "The sudden expansion or the quick evolution in the earlier periods of the earth's history and the slower evolution of the same types in their progressive history, after a period of sudden expansion had been passed through," were shown in several series.