64 ANNALS' NEW YORE ACADEMY OF SCIENCES 



Given then this duplication of environmental complexes and given also 

 the same common generalized widely distributed genera of Cichlidas, may 

 we not also expect some similar changes in the common germplasm ? 



The Paraguay harbors the following species of ciehlid fishes : 



Chmtobranchopsis anstralis, southern form of C. orbicularis, 



Astronotus ocellata, 



JEquidens paraguayensis, southern form of A. teteramerus, 



portalegrensis, southern form of Cichlasoma bimaculatum, 

 dorsigera, 

 Cichlasoma festivum, 

 Crenicichla simioni, perhaps synonymous with C. reticulata, 



semifasciata, perhaps synonymous with C. cyanonotus, 

 lepidota, southern form of C. saxatilis, 

 vittata, southern form of C. macrophthalmus, 

 Heterogramma twniatum, 



trifasciatum, 



borelli, giving off H. ritense, 

 corumbw, 

 Qeophagus balsami, 

 jurupari. 



Of the sixteen species of Cichlidse, only five are found in Eio Uruguay 

 and Eio Grande do Sul, only three are found in Eio Sao Francisco and 

 only three are found in the Alto Eio Parana and the coastwise streams of 

 southeastern Brazil. These three are widely distributed species. All 

 of these sixteen species excepting five are also found in the Amazon, and 

 of these five, two are Heterogramma, which are connected by intermediate 

 stages in such a way that Heterogramma twniatum can easily give rise to 

 all the species of this genus. Two of the other species which are not 

 found in the Amazon are Crenicichla semifasciata and simoni, but these 

 are still questionable species, and they also may even exist in the Amazon. 

 In order to explain this identity of the Cichlidse, I might even grant that 

 all of these species have in some unknown way interchanged between the 

 Amazon basin and the Paraguay. If, however, I should grant so much 

 as that, I should then find even greater trouble in explaining not only 

 wiry the rest of the Cichlida? of the Guapore were not able to get in the 

 Paraguay, but also why the Paraguayan species have remained identical 

 with those of the Amazon and why the Paraguayan species have not in- 

 vaded the Eio Parana and Eio Uruguay, all of which have navigable 

 channels in their lower courses. In other words, the La Plata basin has a 

 triple ciehlid fauna, and these correspond exactly with the natural en- 

 vironments of the Alto Parana and the coastwise streams of eastern 

 Brazil, Eio Uruguay and Eio Grande do Sul, and Eio Paraguay The 



