28 A JOURNEY IN BRAZIL. 



Their upper part is usually broken by waterfalls, their 

 lower course being more level ; probably in the lower 

 courses of these rivers we shall find fishes similar to those 

 of the short coast streams, while in the higher broken 

 waters we shall find distinct faunas." The lecture closed 

 with some account of the excursions likely to be undertaken 

 in the neighborhood of Rio de Janeiro on arriving, and with 

 some practical instructions about collecting, based upon Mr. 

 Agassiz's personal experience.* 



* On account of the many exploring expeditions for which the Bay of 

 Eio de Janeiro has been a favorite port, it has acquired a special interest for 

 the naturalist. It may seem at first sight as if the fact that French, English, 

 German, Russian, and American expeditions have followed each other in this 

 locality, during the last century, each bringing away its rich harvest of speci- 

 mens, by diminishing its novelty would rather lessen than increase its interest 

 as a collecting ground. On the contrary, for the very reason that the speci- 

 mens from which the greater part of the descriptions and figures contained in 

 the published accounts of these voyages were obtained from Rio de Janeiro 

 and its neighborhood, it becomes indispensable that every zoological museum 

 aiming at scientific accuracy and completeness should have original specimens 

 from that very locality for the identification of species already described. 

 Otherwise doubts respecting the strict identity or specific difference of speci- 

 t mens obtained on other parts of the Atlantic shore, not only in South America 

 but in Central and North America, may at any time invalidate important gen- 

 eralizations concerning the distribution of animals in these seas. From this 

 point of view, the Bay of Rio de Janeiro forms a most important centre of 

 comparison, and it was for this reason that we made so prolonged a stay there. 

 Although the prospect of discovering any novelties was diminished by the 

 extensive investigations of our predecessors, I well knew that whatever we 

 collected there would greatly increase the value of our collections elsewhere. 

 One of my special aims was to ascertain how far the marine animals inhabiting 

 the coast of Brazil to the south of Cape Frio differed from those to the north 

 of it, and furthermore, how the animals found along the coast between Cape 

 Frio and Cape St. Roque differed from or agreed with those inhabiting the 

 more northern shore of the continent and the West Indian Islands. In the 

 course of the following chapters I shall have occasion to return, more in de- 

 tail, to this subject. L. A. 



