PLATE 1 



EXPLANATION OF FIGURES 



Figures 1 to 9 are drawn from whole mounts of the heads. The nerve cell 

 layer is stippled, the fibrous core blank. Oc. 2, obj. AA, Zeiss, table-level, re- 

 duced one-half. 



1 The brain of the queen of Camponotus pennsylvanicus. 



2 The head and brain of the worker of C. pennsylvanicus. 



3 The head and brain of the male of C. pennsylvanicus. 



4 The head and brain of the queen of Formica schaufussi. 



5 The head and brain of the worker of F. schaufussi. 



6 The head and brain of the male of F. schaufussi. 



7 The head and brain of the queen of Lasius niger. 



8 The head and brain of the worker of L. niger. 



9 The head and brain of the male of L. niger. 



558 



