CHAPTER XII. 



1843-1846 : -ET. 36-39. 



Completion of Fossil Fishes. Followed by Fossil Fishes of 

 the Old Red Sandstone. Review of the Later Work. 

 Identification of Fishes by the Skull. Renewed Corre- 

 spondence with Prince Canino about Journey to the United 

 States. Change of Plan owing to the Interest of the 

 King of Prussia in the Expedition. Correspondence be- 

 tween Professor Sedgwick and Agassiz on Development 

 Theory. Final Scientific Work in Neuchatel and Paris. 

 Publication of "Systeme Glaciaire." Short Stay in 

 England. Sails for United States. 



IN 1843 the " Recherches sur les Poissons 

 Fossiles " was completed, and fast upon its foot- 

 steps, in 1844, followed the author's " Mon- 

 ograph on the Fossil Fishes of the Old Red 

 Sandstone, or the Devonian System of Great 

 Britain and Russia," a large quarto volume of 

 text, accompanied by forty-one plates. Noth- 

 ing in his paleontological studies ever inter- 

 ested Agassiz more than this curious fauna 

 of the Old Red, so strange in its combinations 

 that even well-informed naturalists had attrib- 

 uted its fossil remains to various classes of 

 the animal kingdom in turn, and, indeed, long 



