But it is upon the construction of the bottoms of the intermediate ranges of cells that this variation of their architecture chiefly hinges. The bottoms of the regular cells of bees are, as you are aware, composed of three equal-sized rhomboidal pieces; and the base of a cell on one side of the comb is composed of portions of the bases of three cells on the other; but the bottoms of the intermediate cells in question (though their orifices are perfectly hexagonal) are composed of four pieces, of which two are hexagonal and two rhomboidal; and each, instead of corresponding with three cells on the opposite side, corresponds with four. The size and the shape of the four pieces composing the bottom, vary; and these intermediate cells, a little larger than the third part of the three opposite cells, comprise in their contour a portion of the bottom of the fourth cell. Just below the last range of cells with regular pyramidal bottoms, are found cells with bottoms of four pieces, of which three are very large, and one very small, and this last is a rhomb. The two rhombs of the transition cells are separated by a considerable interval; but the two hexagonal pieces are adjacent and perfectly alike. A cell lower, we perceive that the two rhombs of the bottom are not so unequal: the contour of the cell has included a greater portion of the opposite fourth cell. Lastly, we find cells in pretty considerable number, of which the bottom is composed of four pieces perfectly regular—namely, two elongated hexagons and two equal rhombs, but smaller than those of the pyramidal bottoms. In proportion as we remove our view from the cells with regular tetrahedral bottoms, whether in descending or from right to left, we see that the subsequent cells resume their ordinary form; that is to say, that one of their rhombs is gradually lessened until it finally disappears entirely; and the pyramidal form re-exhibits itself, but on a larger scale than in the cells at the top of the comb. This regularity is maintained in a great number of ranges, namely, those consisting of male cells; afterwards the cells diminish in size, and we again remark the tetrahedral bottoms just described, until the cells have once more resumed the proper diameter of those of workers.
It is, then, by encroaching in a small degree upon the cells of the other face of the comb, that bees at length succeed in giving greater dimensions to their cells; and the graduation of the transition cells being reciprocal on the two faces of the comb, it follows that on both sides each hexagonal contour corresponds with four cells.—When the bees have arrived at any degree of this mode of operating, they can stop there and continue to employ it in several consecutive ranges of cells: but it is to the intermediate degree that they appear to confine themselves for the longest period, and we then find a great number of cells of which the bottoms of four pieces are perfectly regular. They might, then, construct the whole comb on this plan, if their object were not to revert to the pyramidal form with which they set out.—In building the male cells, the bees begin their foundation with a block or mass of wax thicker and higher than that employed for the cells of workers, without which it would be impracticable for them to preserve the same order and symmetry in working on a larger scale.
Irregularities (to use the language of Huber, from whom the above details are abstracted,) have often been observed in the cells of bees. Reaumur, Bonnet and other naturalists cite them as so many examples of imperfections. What would have been their astonishment if they had been aware that part of these anomalies are calculated; that there exists as it were a moveable harmony in the mechanism by which the cells are composed! If, in consequence of the imperfection of their organs or of their instruments, bees occasionally constructed some of their cells unequal, or of parts badly put together, it would still manifest some talent to be able to repair these defects, and to compensate one irregularity by another: but it is far more astonishing that they know how to quit their ordinary routine when circumstances require that they should build male cells; that they should be instructed to vary the dimensions and the shape of each piece so as to return to a regular order; and that, after having constructed thirty or forty ranges of male cells, they again leave the regular order on which these were formed, and arrive by successive diminutions at the point from which they set out. How should these insects be able to extricate themselves from such a difficulty—from such a complicated structure? how pass from the little to the great, from a regular plan to an irregular one, and again resume the former? These are questions which no known system can explain[784].
Here again, as observed in a former instance, the wonder would be less, if every comb contained a certain number of transition and of male cells, constantly situated in one and the same part of it: but this is far from being the case. The event which alone, at whatever period it may happen, seems to determine the bees to construct male cells, is the oviposition of the queen. So long as she continues to lay the eggs of workers not a male cell is founded; but as soon as she is about to lay male eggs, the workers seem aware of it, and you then see them form their cells irregularly, impart to them by degrees a greater diameter, and at length prepare suitable ranges of cradles for all the male race[785].—You must perceive how absurd it would be to refer this astonishing variation of instinct to any mere change in the sensations of the bees; and to what far-fetched and gratuitous suppositions we must be reduced, if we adopt any such explanation. We can but refer it to an instinct of which we know nothing; and so referring it, can we help exclaiming with Huber, "Such is the grandeur of the views and of the means of ordaining wisdom, that it is not by a minute exactness that she marches to her end, but proceeds from irregularity to irregularity, compensating one by another: the admeasurements are made on high, the apparent errors appreciated by a divine geometry; and order often results from partial diversity. This is not the first instance which science has presented to us of preordained irregularities which astonish our ignorance, and are the admiration of the most enlightened minds: So true it is, that the more we investigate the general as well as particular laws of this vast system, the more perfection does it present[786]."
It is observed by M. P. Huber, in his appendix to the account of his father's discoveries relative to the architecture of bees, that in general the form of the prisms or tubes of the cells is more essential than that of their bottoms, since the tetrahedral-bottomed transition cells, and even those cells which being built immediately upon wood or glass, were entirely without bottoms, still preserved their usual shape of hexagonal prisms. But a remarkable experiment of the elder Huber shows that bees can alter even the form of their cells when circumstances require it, and that in a way which one would not have expected.
Having placed in front of a comb which the bees were constructing, a slip of glass, they seemed immediately aware that it would be very difficult to attach it to so slippery a surface: and instead of continuing the comb in a straight line, they bent it at a right angle, so as to extend beyond the slip of glass, and ultimately fixed it to an adjoining part of the wood-work of the hive which the glass did not cover. This deviation, if the comb had been a mere simple and uniform mass of wax, would have evinced no small ingenuity; but you will bear in mind that a comb consists on each side, or face, of cells having between them bottoms in common: and if you take a comb, and having softened the wax by heat, endeavour to bend it in any part at a right angle, you will then comprehend the difficulties which our little architects had to encounter. The resources of their instinct, however, were adequate to the emergency. They made the cells on the convex side of the bent part of the comb much larger, and those on the concave side much smaller than usual; the former having three or four times the diameter of the latter. But this was not all. As the bottoms of the small and large cells were as usual common to both, the cells were not regular prisms, but the small ones considerably wider at the bottom than at the top, and conversely in the large ones!—What conception can we form of so wonderful a flexibility of instinct? How, as Huber asks, can we comprehend the mode in which such a crowd of labourers, occupied at the same time on the edge of the comb, could agree to give to it the same curvature from one extremity to the other; or how they could arrange together to construct on one face cells so small, while on the other they imparted to them such enlarged dimensions?—And how can we feel adequate astonishment that they should have the art of making cells of such different sizes correspond[787]?
After this long but I flatter myself not wholly uninteresting enumeration, you will scarcely hesitate to admit that insects, and of these the bee pre-eminently, are endowed with a much more exquisite and flexible instinct than the larger animals. But you may be here led to ask, Can all this be referred to instinct? Is not this pliability to circumstances—this surprising adaptation of means for accomplishing an end—rather the result of reason?
You will not doubt my allowing the appositeness of this question, when I frankly tell you, that so strikingly do many of the preceding facts seem at first view the effect of reason, that in my original sketch of the letter you are now reading, I had arranged them as instances of this faculty. But mature consideration has convinced me (though I confess the subject has great difficulties) that this view was fallacious; and that though some circumstances connected with these facts may, as I shall hereafter show, be referable to reason, the facts themselves can only be consistently explained by regarding them as I have here done, as examples of variations of particular instincts:—and this on two accounts.