按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
Such are the facts； though they did not need confirmation by me； in regard to the wonderful instinct of making slaves。 Let it be observed what a contrast the instinctive habits of F。 sanguinea present with those of the F。 rufescens。 The latter does not build its own nest； does not determine its own migrations； does not collect food for itself or its young； and cannot even feed itself： it is absolutely dependent on its numerous slaves。 Formica sanguinea； on the other hand； possesses much fewer slaves； and in the early part of the summer extremely few。 The masters determine when and where a new nest shall be formed； and when they migrate； the masters carry the slaves。 Both in Switzerland and England the slaves seem to have the exclusive care of the larvae； and the masters alone go on slave…making expeditions。 In Switzerland the slaves and masters work together； making and bringing materials for the nest： both； but chiefly the slaves； tend； and milk as it may be called； their aphides； and thus both collect food for the community。 In England the masters alone usually leave the nest to collect building materials and food for themselves； their slaves and larvae。 So that the masters in this country receive much less service from their slaves than they do in Switzerland。
By what steps the instinct of F。 sanguinea originated I will not pretend to conjecture。 But as ants； which are not slave…makers； will； as I have seen； carry off pupae of other species； if scattered near their nests； it is possible that pupae originally stored as food might become developed； and the ants thus unintentionally reared would then follow their proper instincts； and do what work they could。 If their presence proved useful to the species which had seized them if it were more advantageous to this species to capture workers than to procreate them the habit of collecting pupae originally for food might by natural selection be strengthened and rendered permanent for the very different purpose of raising slaves。 When the instinct was once acquired； if carried out to a much less extent even than in our British F。 sanguinea； which； as we have seen； is less aided by its slaves than the same species in Switzerland； I can see no difficulty in natural selection increasing and modifying the instinct always supposing each modification to be of use to the species until an ant was formed as abjectly dependent on its slaves as is the Formica rufescens。
Cell…making instinct of the Hive…Bee。 I will not here enter on minute details on this subject； but will merely give an outline of the conclusions at which I have arrived。 He must be a dull man who can examine the exquisite structure of a comb； so beautifully adapted to its end； without enthusiastic admiration。 We hear from mathematicians that bees have practically solved a recondite problem； and have made their cells of the proper shape to hold the greatest possible amount of honey； with the least possible consumption of previous wax in their construction。 It has been remarked that a skilful workman； with fitting tools and measures； would find it very difficult to make cells of wax of the true form； though this is perfectly effected by a crowd of bees working in a dark hive。 Grant whatever instincts you please； and it seems at first quite inconceivable how they can make all the necessary angles and planes； or even perceive when they 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 very simple instincts。
I was led to investigate this subject by Mr。 Waterhouse； 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 this 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 know； is an hexagonal prism； with the basal edges of its six sides bevelled so as to join on to a pyramid； formed 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 perfection 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 spherical and of nearly equal sizes； and are aggregated into an irregular mass。 But the important point to notice； is that these cells are always made at that degree of nearness to each other； that they would have intersected or broken into each other； if the spheres had been completed； but this is never permitted； the bees building perfectly flat walls of wax between the spheres which thus tend to intersect。 Hence each cell consists of an outer spherical portion and of two； three； or more perfectly flat surfaces； according as the cell adjoins two； three or more other cells。 When one cell comes into contact with three other cells； which； from the spheres 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 basis of the cell of the hive…bee。 As in the cells of the hive…bee； so here； the three plane surfaces in any one cell necessarily enter into the construction of three adjoining cells。 It is obvious that the Melipona saves wax by this manner of building； for the flat walls between the adjoining cells are not double； but are of the same thickness as the outer spherical portions； and yet each flat portion forms a part of two cells。
Reflecting on this case； it occurred to me that if the Melipona had made its spheres at some given distance from each other； and had made them of equal sizes and had arranged them symmetrically in a double layer； the resulting structure would probably have been as perfect as the comb of the hive…bee。 Accordingly I wrote to Professor Miller； of Cambridge； and this geometer has kindly read over the following statement； drawn up from his information； and tells me that it is strictly correct：…
If a number of equal spheres be described with their centres placed in two parallel layers； with the centre of each sphere at the distance of radius X /sqrt＇2＇ or radius X 1。41421 （or at some lesser distance）； from the centres of the six surrounding spheres in the same layer； and at the same distance from the centres