THE AMERICAN TETRAGONOPTERINAE. 



45 



to examine hundreds of specimens from the Amazon, not one of which showed 

 signs of mutation, while the specimens coming from another region are in an 

 evident state of mutation. 



Genera with a complete lateral line and the genera with an incomplete 

 lateral line to which they have given rise are : — 



The deviation is so evident in a number of cases that the polyphyletic origin 

 of the character 6, an incomplete lateral line, is beyond the faintest shadow of a 

 doubt. 



Without considering sporadic individuals of otherwise constant species, 

 the species which are undoubtedly mutuating at the present time are Hemi- 

 grammus inconstans, Moenkhausia cotinho, Phenacogaster beni, Astyanax mutator, 

 and Hyphessobrycon poecilioides. The details for these species are given under 

 their descriptions. Another species which has crossed the line but has not 

 reached a state of equilibrium is Psellogrammus kennedyi. Many of the details 

 of this species are again given under the proper caption. 



Of Ctenobrycon hauxwellianus I have been able to examine over fourteen 

 hundred specimens from various places on the Amazon. In all of these the 

 lateral line is complete. In at least six specimens out of nineteen from the Lagoa 



