LIFE IN TEFFfi. 



221 



and he has gathered a good deal of information about its 

 habits. The fishermen here say that this mode of caring 



dent manner by Heckel and J. Miiller. But, beside these, there are the genera 

 Enoplosus, Poraotis, Centrarchus, and some other neighboring genera, classed 

 among the Percoids by all Ichthyologists, which seem to me, from this distance 

 and without means of direct comparison, so near the Chromides that I do not 

 see how they can be separated, especially now that I know the lower pharyn- 

 gials not to be invariably soldered in the Chromides. And then the embryol- 

 ogy and metamorphoses of the Chromides, which I have just been studying, 

 have convinced me that the fishes with labyrinthic branchije, separated from all 

 other fishes by Cuvier, as a family entirely isolated on account of the strange 

 structure of its respiratory organs, are closely related to the Chromides. Thus 

 this group becomes, by its various affinities, one of the most interesting of the 

 class of fishes, and the basin of the Amazons seems to be the true home of this 

 family. I will not fatigue you with my ichthyological researches ; let me only 

 add, that the fishes are not uniformly spread over this great basin. I have 

 already acquired the certainty that we must distinguish several ichthyological 

 faunae very clearly characterized. Thus the species inhabiting the river of 

 Para, from the borders of the sea to the mouth of the Tocantins, differ from 

 those which are met in the network of anastomoses uniting the river of Para 

 with the Amazons proper. The species of the Amazons below the Xingu 

 differ from those which occur higher up ; those of the lower course of the 

 Xingu differ from those of the lower course of the Tapajoz. Those of the 

 numerous igarapes and lakes of Manaos differ as much from those of the 

 principal course of the great river and of its great affluents. It remains now 

 to study the changes which may take place in this distribution in the course 

 of the year, according to the height of the waters, and perhaps also accord- 

 ing to the epoch at which the different species lay their eggs. Thus far I 

 have met but a small number of species having a very extensive area of dis- 

 tribution. One of those is the Sudis gigas, found almost everpvhere. It is 

 the most important fish of the river, that which, as food, corresponds to cattle 

 for the population along the banks. Another problem to be solved is, how far 

 this phenomenon of the local distribution of fishes is repeated in the great 

 aflSuents of the Amazons. I shall try to solve it in ascending the Rio Negro 

 and Rio Madeira, and as I return to Manaos I shall be able to compare my 

 first observations in this locality with those of another season of the year. 

 Adieu, my dear friend. Remember me to M. Elie de Beaumont and to those 

 of my colleagues of the Academy who are interested in my present studies. 

 My kind remembrance also to your son. 



Always yours, 



L. Agassiz 



