■and on the Origin of Species. 305 



have his readers believe that this absurdity is maintained by the 

 writers he alludes to. 



The author then describes the following three forms of cells 

 which he has observed, but does not always express his meaning 

 with sufficient accuracy: — 1. Hexagonal cells, somewhat pyra- 

 midal, with a rounded extremity. The British tree-wasp and 

 the genus Polistes make cells of this form, in small groups, and 

 often of a very fragile papery material. 2. " Hexagonal cells 

 formed of adjoining prismatic figures, with rectilinear axes, ter- 

 minated by a truncated plane, at right angles to the axes of the 

 prisms.^' I have quoted this elaborate description literally, be- 

 cause I am quite unable to understand what the author means 

 by a " truncated plane," which renders his meaning somewhat 

 obscure. The cells of this form are said to occur in wasps' 

 nests from the West Indies and South Africa. 3. The bee's 

 hexagonal cell terminated by three faces of a rhombic dodeca- 

 hedron, each of which forms one-third of the base of one of the 

 cells of the opposite layer. It is not stated, but may be inferred, 

 tliat the first two forms of cells are in a single layer only; and 

 all these varieties of cells, it is said, may be accounted for 

 " simply by the mechanical pressure of the insects against each 

 other during the formation of the cell.'' Again, at page 428, 

 " The true cause of the shape of the cell is the crowding together 

 of the bees at work, as was first shown by Buifon. From this 

 crowding together they cannot help making cells with the di- 

 hedral angles of 120° of the rhombic dodecahedron; and the 

 economy of wax has nothing to do with the origin of the cell, 

 but is a geometrical property of the figure named." There are, 

 howevei', several important objections to this pressure-theory. 

 Many exotic tree-wasps construct little groups of three or four 

 hexagonal cells, only one or two insects working at them toge- 

 ther. Here is no crowding, yet they are hexagonal. Again, a 

 Mexican bee [Melipona domestica) makes a comb of cylindrical 

 cells, only partially hexagonal; and in the Malay Islands there 

 is a domesticated bee which makes oval cells, and though the 

 insects are kept in hollow bamboos for hives, yet the crowding 

 together does not make their cells hexagonal. The wild bee of 

 Borneo, on the other hand, suspends its comb from the arms of 

 lofty trees in the free air ; and if crowding had all and economy 

 nothing to do with it, one would think that here the cells should 

 retain their normal cylindrical form ; instead of which, they 

 are as beautifully geometrical as those of our own hive-bee. 

 But, what is still more important, Mr. Darwin states (Origin of 

 Species, ed. 3, p. 251) that our bees build the cell-wall at first 

 rough and ten times as thick as it is to remain when finished, 

 it being afterwards gnawed down to the proper thinness. Here 



