xxvii 



two terms, when he was compelled by the state of his health to give up 

 the appoiutment. 



In 1853 he published a paper on the newly discovered viviparous fishes 

 of California, and also began to work up the vast amount of materials 

 which he had collected in America. The publications of the American 

 Academy of Boston, of the Boston Society of Natural History, and of the 

 American Association for the Advancement of Science contain a large 

 number of papers on the Natural History of the United States. He was 

 also for many years an active contributor to the pages of the ' American 

 Journal of Arts and Sciences.' He sketched out a series of essays, 

 which were to be entitled " Contributions to the Natural History of the 

 United States." 2500 names appeared on the subscription list of this 

 work. He hoped to publish ten A^olumes of this series, but only actually 

 published four, leaving a fifth unfinished. These four are : — An Essay 

 on Classification ; North- American Testudinata ; the Embryology of 

 Turtles ; and ' The Acalephs,' under which were included Monographs 

 of the Ctenophorae, Discophorge, and Hydroidse, and an essay on the 

 Homologies of the Eadiata. His chief assistant in their preparation 

 was the late Prof. H. J. Clark. These books were illustrated by first- 

 rate lithographic plates, the best of which were drawn by Sonrel. 



The ' Essay on Classification ' is the crowning work of Agassiz. The 

 erudition displayed in this work is remarkable, and the grasp of facts, 

 intricate and numerous in their relations, is quite amazing. In nothing 

 is this better exhibited than in his celebrated demonstration of embryo- 

 logical, geological, and zoological succession. He shows that in many 

 orders the species which first appear in the older beds resemble the embryo 

 of the highest species now living ; and, moreover, that this fossil and this 

 embryo have characteristics in common with the living species that stand 

 lower in the zoological scale. Thus, among living Crustacea, the Brachy- 

 urans stand highest ; but the embr3^o of the Brachyuran has a long tail 

 like the Macrurans, which are characteristic of the middle geological 

 periods, and the living forms of which are zoologically inferior to the 

 Brachyurans. 



The last years of Agassiz's life were devoted to founding a large museum 

 arranged to show his views of the relations of living animals among 

 themselves, and their connexions in the geological and embrj^ological 

 successions. 



His own collections, which had gradually outgrown the means of a single 

 individual, formed the nucleus of a Museum of Comparative Zoology. 

 An endowment-fund was commenced by the generosity of one of his 

 friends, Mr. E. C. Gray, the cooperation of Harvard College and the 

 State of Massachusetts adding to its means at different times. On the 

 death of Agassiz a "Memorial Eund" was raised by subscription, ample 

 enough, it is hoped, to carry out some at least of his cherished ideas. 



This Museum has been the nursery for nearly all the Professors of 



