144 Psyche [October 



other genus of ants possessing well-developed eyes in the normal 

 workers. The workers of Aphanogaster bakeri, like those of all 

 the species of the genus, are monomorphic or very feebly poly- 

 morphic, and the eyes, though not large, are nevertheless well 

 developed. The exceptional specimen is in all respects normal 

 except in the shape of the head and the absence of visual organs. 



a. Head of normal worker of Aphoenogaster patruelis Forel 

 var. bakeri Wheeler, b. Head of eyeless worker of 

 same. 



The head, as will be seen from a comparison of the figures, is sub- 

 oblong and the sides, especially at the middle, are very distinctly 

 concave, probably owing to an absence of the optic ganglia. On 

 the left side the integument, where the eye should be, is slightly 

 rugose and presents what appears to be a single minute, pigmented 

 ommatidium; on the right side the integument in the correspond- 

 ing concavity is smooth and rather pale. That the eyeless indi- 

 vidual had been living and working for some time like its normal 

 sisters is shown by its mature coloration and the blunted teeth of 

 its mandibles. 



As colonies of Aphoenogaster contain, as a rule, only a single 

 fertile queen, it is very probable that the anomalous specimen 

 above described and the normal workers are all daughters of the 

 same mother. We may, therefore, assume that the eyeless worker 

 is a mutation, strictly comparable with the eyeless specimens that 

 have appeared in certain cultures of the fly Drosophila, and we 

 might infer that the normally eyeless workers and females of such 

 ant genera as Doryhis and the corresponding phases of certain 

 species of Eciton, in which the eye is reduced to a single omma- 

 tidium, arose as similar mutations. We might be tempted, more- 

 over, to extend this inference to other peculiarities of worker ants, 



