PROFESSOR LOUIS AGASSIZ. 611 



and Disaster, by Desor ; and the fifth, on the Anatomy of Echinus, by 

 Valentin. Among the Scutellse Agassiz found well-marked differences 

 between the living and fossil species, and that all the species of the 

 genera Mellita, Rotula, and JEncope, belong to the existing epoch. 

 He found, moreover, that the species increase in size as they approach 

 the present period. While he was publishing his work on the Echino- 

 derms, this indefatigable naturalist also described and figured a large 

 collection of fossil shells from the Oolite and Cretaceous formations, in 

 a work entitled " Etudes critique sur les Mollusques de Jura et de la 

 Craie," besides an annotated German translation of Buckland's " Ge- 

 ology," and French and German translations of Sowerby's "Mineral 

 Conchology." 



Notwithstanding the immense amount of work on his hands, Ag- 

 assiz found time to prosecute his investigation upon the fresh-water 

 fishes of Europe. The first part of this work, issued in 1839, is de- 

 voted to the genera Salmo and Thymallus. It appears as a folio of 

 twenty-seven excellent plates, with descriptions illustrating six species 

 of Salmo and one of Thymallus, one plate of each species being colored 

 according to life, the others representing differences of age, sex, and 

 locality. The second part, which did not appear till 1842, consists of 

 a folio of plates and a volume of text on the "Embryology of the 

 Salmons," by Carl Vogt, whom Agassiz had associated with him in his 

 work. M. Vogt has given the most detailed descriptions and figures 

 of the different organs, and the changes they undergo from the for- 

 mation of the cellules, out of .which the organs are developed, to the 

 adult state. In regard to cell-formation, M. Vogt differs from Schwann 

 in affirming that the germinative vesicle is formed prior to the nuclei 

 and nucleoli. The volume closes with a history of the daily develop- 

 ment of the embryo, from the exclusion of the egg to the birth of the 

 young. This excellent work was never completed ; Agassiz's depart- 

 ure for the United States shortly after, and his increasing responsi- 

 bilities, prevented the perfection of his orignal plan. 



In 1842 Agassiz began the publication of his " Nomenclator Zo- 

 ologicus," an alphabetical list of every genus, with the name of the 

 author, the work in which it originally appeared, the derivation of the 

 name, and the family to which the genus belongs ; the list embracing 

 upward of seventeen thousand names. In the introduction the author 

 examines the rules proposed by the British Association and those of 

 the British Committee. He agrees with the rules proposing that the 

 name given by a founder of a group, or the first describer of a species, 

 should be retained, and that priority is to be conceded only to a 

 name published in some universally accessible work. On the other 

 hand, he objects to the restriction of priority to Linnseus and to the 

 rule that would change a name previously in use in connection with 

 some other genus in zoology or botany, as this would result in the 

 sacrifice of half the names of recent times. He does not think it wise 



