316 PROCEEDINGS OF THE AMERICAN ACADEMY 



that year directions to fishermen for the impregnation of fish eggs, — an 

 event which antedates the rediscovery of pisciculture by Remy. 



Agassiz did not, at that time, pursue further these observations; but 

 it is plain that he pondered them much, and that they recalled the 

 teachings of his good master, Dolliuger, on the relations of embryology 

 to zoology. His reflection was to take form some years later, and to 

 throw new light on the intricate question of animal succession. 



Echinoderms attracted the attention of Agassiz almost as early as fishes. 

 His paper tJber die Echinodermen appeared in the "Isis" in 1834, and 

 in 1839 he published an admirable anatomical essay on Astrophyton. 

 Doubtless the peculiar plan of structure of this class, so simple in theory 

 and so varied in practice, struck him as one which might be intelligible, 

 and might give solid points from which to approach the more complex 

 plans. To these considerations was added the advantage of a wide distri- 

 bution both of the living and the fossil representatives. However it may 

 be, he pushed the investigations of Echinodermata with extraordinary 

 energy and thoroughness, and vras aided in the task by Desor. From 

 1838 to 1842 there appeared his Monographies d' Echinodermes vivans 

 etfossiles, including a remarkable anatomy of the common sea-urchin, 

 by Valentin. The preparation of this standard work was connected 

 with some of Agassiz's happiest days, when he used to visit Paris for 

 the sake of the great collections at the Garden of Plants, and for inter- 

 course with the eminent men of science who were gathered there. And 

 now, at the age of thirty-five, he had already put forth books on fishes, 

 mollusks, and echinoderms, and on the geology of the drift period, any 

 one of which would have given a reputation. During his fifteen years 

 of arduous study, he had, with a care for detail scarcely to be expected 

 in so ardent a character, prepared long lists of the generic names which 

 occurred in his reading ; and he conceived the idea of«extending these lists 

 so as to include the known genera of the entire animal kingdom. The 

 work was revised and enlai-ged by twenty-two colleagues, each of 

 whom took a group ; and the whole was completed in 1846, under the 

 name of Nomenclator Zoblogicus. It was as if the author had come to 

 a period in his labors, and had made an index ; for there was presently 

 to be a change in his life and in his home. 



At the suggestion of Lyell, Mr. John A. Lowell had, in 1845, 

 invited Professor Agassiz to come to Boston and deliver lectures before 

 the Lowell Institute. About the same time the King of Prussia, 

 through the ever-thoughtful mediation of Humboldt, had jDresented 

 him with a sum of money in aid of a scientific mission to America. 

 Thus encouraged by invitation and by pecuniary aid, he crossed the 



