540 



THE FORMS OF TISSUES 



[CH. 



But the spherical form is only seen on the outside of the mass; 

 for inwardly each cell is flattened into "two, three or m.ore flat 

 surfaces, according as the cell adjoins two, three or more other cells. 

 When one cell rests on three other cells, which from the spheres 



Fig. 209. An early stage of a wasp's nest. Observe the spherical caps, and the 

 irregular shape of the peripheral cells. After R. Bott. 



being nearly of the same size is very frequently and necessarily the 

 case, the three flat surfaces are united into a pyramid; and this 

 pyramid, as Huber has remarked, is manifestly a gross imitation 

 of the three-sided pyramidal base of the cell of the hive-bee*." 



* Origin of Species, ch. viii (6th ed., p. 221). The cells of various bees, humble- 

 bees and social wasps have been described and mathematically investigated by 

 K. MiillenhofF, Pfiuger's Archiv, xxxii, p. 589, 1883; but his many interesting 

 results are too complex to .epitomise. For figures of various nests and combs see 

 (e.g.) von Buttel-Reepen, Biol. Centralbl. xxxm, pp.. 4, 89, 129, 183, 1903. 



