Chap. Vm.] CELL-MAKING INSTINCT. 343 



are correctly made. But the difficulty is not nearly so 

 great as it at first appears : all this beautiful work 

 can be shown, I think, to follow from a few simple 

 instincts. 



I was led to investigate this subject by Mr. Water- 

 house, who has shown that the form of the cell stands in 

 close relation to the presence of adjoining cells ; and the 

 following view may, perhaps, be considered only as a 

 modification of his theory. Let us look to the great 

 principle of gradation, and see whether Nature does not 

 reveal to us her method of work. At one end of a short 

 series we have humble-bees, which use their old cocoons 

 to hold honey, sometimes adding to them short tubes of 

 wax, and likewise making separate and very irregular 

 rounded cells of wax. At the other end of the series we 

 have the cells of the hive-bee, placed in a double layer : 

 each cell, as is well known, is an hexagonal prism, with 

 the basal edges of its six sides bevelled so as to join an 

 inverted pyramid, of three rhombs. These rhombs have 

 certain angles, and the three which form the pyramidal 

 base of a single cell on one side of the comb enter into 

 the composition of the bases of three adjoining cells on 

 the opposite side. In the series between the extreme per- 

 fection of the cells of the hive-bee and the simplicity of 

 those of the humble-bee we have the cells of the Mexican 

 Melipona domestica, carefully described and figured by 

 Pierre Huber. The Melipona itself is intermediate 

 in structure between the hive and humble bee, but 

 more nearly related to the latter ; it forms a nearly 

 regular waxen comb of cylindrical cells, in which the 

 young are hatched, and, in addition, some large cells of 

 wax for holding honey. These latter cells are nearly 

 sj)herical and of nearly equal sizes, and are aggregated 



