English ichthyologist withdrew from active life. Meanwhile the 

 expeditions fitted out by Austria and Prussia, each accompanied by 

 a staff of naturalists, brought large collections of fishes to the Berlin 

 and Vienna Museums; in St. Petersburg collections made in North- 

 eastern Asia are accumulating ; Dr. Bleeker, who has made us 

 acquainted with the astonishing variety of fishes in the East-Indian 

 archipelago, could not have succeeded so well Avithout the cordial 

 cooperation of the officials residing in the various islands ; Messrs. 

 Godeffroy, wealthy merchants of Hamburgh, have founded, merely 

 by the assistance of the captains of their o^Yn ships and of two or 

 three collectors, a private museum which supplies now annually 

 other public collections with a great number of rare or quite new 

 forms from the various parts of the Pacific ; in the United States 

 each exploring expedition was and still is accompanied by naturalist 

 collectors, employed solely for the benefit of public museums ; and, 

 finally. Prof. Agassiz himself has explored the ichthyology of the 

 River Amazons, and returned with a booty the richness of which is 

 great, though not yet exactly defined. 



" Thus there cannot be any doubt with regard to the activity put 

 forth in the field of ichthyology ; and it is a fact that the foremost 

 men in science have devoted a great proportion of their researches 

 to this branch, — and justly so. No other class of vertebrates offers 

 a similar gradation of development of the most important systems 

 and organs, rendering its systematic arrangement one of the most 

 difficult problems of zoology. Infinite are those modifications of 

 organs which may be brought into connexion Avith the variations of 

 their mode of life and with the M-idely different physical conditions 

 under which fishes live. There is no fresh water, no sea, no part of 

 the sea which is not inhabited by fishes, some kinds being restricted 

 to an insignificant pool, whilst others roam over the ,vhole extent 

 of the various oceans, or are organized to exist under the pressure 

 of great depths, the same species living in the Atlantic, North 

 Pacific, and Antarctic. The freshwater forms being limited to the 

 river- or lake-systems which they inhabit, and being less exposed to 

 the disturbances affecting the terrestrial animals, are singularly 

 adapted for the elucidation of the original geographical distribu- 

 tion of the animals of the present creation. No other class of the 

 vertebrates is of ecjual imjjortance to the geologist nnd i)al;contf _ 



