464 



POPULAR SCIENCE MONTHLY. 



Coniuhtld. I'l'ofc'ssor Hyatt Avas assisted in giving* these lessons 

 1)Y 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 Xatural flistory Society, and 

 discovered a form of paleozoic Echinoderrn, which proved to be an 

 interesting new species and was described by Dr. Jackson as Lepi- 

 desthes Wo7't]ieni. 



The third year of this series consisted of lessons on B rachiopoda 

 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 in- 

 vestigating Brachiopoda, and 

 communications from him 

 regarding this group were 

 from time to time read to the 

 class. ■' The sudden expan- 

 sion or the quick evolution 

 in the earlier periods of the 

 earth's history and the slow- 

 er evolution of the same 

 types in their progressive his- 

 tor}^, after a period of sud- 

 den expansion had been 

 passed through," were shown 

 in several series. 



Tlie ancestral form of 

 this group, the i)liylembryo, 

 has been found in Paterina, 

 whose adult represents the 

 youngest stage, the beak of 

 the blicll, of other Brachiopods. U'here 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 develop- 

 ment by Professor Hyatt in his writings on bioplastologv were ex- 

 l)lained to and used by the class. 



The many specimens used in this study were Ciii-ct'iilly iigiirccl 

 in the notebooks, and the teachers became so familiar with them 

 that they wci-c altle to pass at the end of the term a severe exami- 



J. Walter Fewkes. 



