Page:Popular Science Monthly Volume 55.djvu/482

464 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.

The ancestral form of this group, the phylembryo, has been found in Paterina, whose adult represents the youngest stage, the beak of the shell, of other Brachiopods. There was, therefore, unusual opportunity to here illustrate theories of evolution, particularly the theory of constitutional tendency involving a conception of the youth, maturity, and senescence of species. In order to make the instruction clearer, terms used for the different stages of development by Professor Hyatt in his writings on bioplastology were explained to and used by the class.

The many specimens used in this study were carefully figured in the notebooks, and the teachers became so familiar with them that they were able to pass at the end of the term a severe