586 



HOMES WITHOUT HANDS. 



Mischocyttarua. 



Raphigaster. 



agitated. It is made by an insect belonging to the genus Icaria. 

 Perhaps my readers may remember that on page 450 the cele- 

 brated bee-cell problem is described, and that mention is made of 

 the many theories which have been invented to solve the riddle. 

 Among them the two most conspicuous are those which are known 

 as the equal pressure theory and the excavation theory. Differing 

 as they do in many respects — one attempting to prove that each 

 cell is forced into the hexagonal shape by the pressure of six cells 

 surrounding it, and the other that the cell is made hexagonal by 

 the cutting away of material from six surrounding cells — they 

 both agree in one point, namely, that the normal shape of the cell 

 is cylindrical, and that it only assumes the hexagonal form by 

 mechanical means. 



These questions were briefly mentioned, because an entire omis- 

 sion of them would appear negligent, but they were not followed 



