The Distribution of the Sexes 



greater stability for her edifice in the sup- 

 port given her by the double plane. These 

 sites appear to me to be in great request with 

 the Chalicodoma, considering the number of 

 nests which I find thus doubly supported. In 

 nests of this kind, all the cells, as usual, have 

 their foundations fixed to the horizontal sur- 

 face; but the first row, the row of cells first 

 built, stands with its back against the vertical 

 surface. 



Well, those older cells, which occupy the 

 actual edge of the dihedral angle, are always 

 female, with the exception of those at either 

 end of the row, which, as they belong to the 

 outside, may be male cells. In front of this 

 first row come others. The female cells oc- 

 cupy the middle portion and the male the 

 ends. Finally, the last row, closing In the 

 remainder, contains only male cells. The 

 progress of the work Is very visible here: the 

 Mason has begun by attending to the central 

 group of female cells, the first row of which 

 occupies the dihedral angle, and has finished 

 her task by distributing the male cells round 

 the outside. 



If the perpendicular face of the dihedral 

 angle be high enough, it sometimes happens 



115 



