PREFACE. 



IN the winter of 1865 it became necessary for me, on 

 account of some disturbance of my health, to seek a change 

 of scene and climate, with rest from work. Europe was 

 proposed ; but though there is much enjoyment for a 

 naturalist in contact with the active scientific life of 

 the Old World, there is little intellectual rest. Toward 

 Brazil I was drawn by a lifelong desire. After the death 

 of Spix, when a student of twenty years of age, I had 

 been employed by Martins to describe the fishes they 

 had brought back with them from their celebrated Bra 

 zilian journey. From that time, the wisli to study this 

 fauna in the regions where it belongs had been an 

 ever-recurring thought with me ; a scheme deferred for 

 want of opportunity, but never quite forgotten. The fact 

 that the Emperor of Brazil was deeply interested in oil 

 scientific undertakings, and had expressed a warm sym 

 pathy with my efforts to establish a great zoological 

 museum in this country, aiding me even by sending 

 collections made expressly under his order for the pur 

 pose, was an additional incentive. I knew that the head 

 of the government would give me every facility for my 

 investigations. Nevertheless, tempting as was the pros- 



