Certain objections arise to affirm that, in this instance, the tool is not the sole regulator of the work.  Were the arrangement of the thread determined by the length of the legs, we should find the spiral volutes separated more widely from one another in proportion to the greater length of implement in the spinstress.  We see this in the Banded Epeira and the Silky Epeira.  The first has longer limbs and spaces her cross-threads more liberally than does the second, whose legs are shorter.

But we must not rely too much on this rule, say others.  The Angular Epeira, the Paletinted Epeira and the Cross Spider, all three more or less short-limbed, rival the Banded Epeira in the spacing of their lime-snares.  The last two even dispose them with greater intervening distances.

We recognize in another respect that the organization of the animal does not imply an immutable type of work.  Before beginning the sticky spiral, the Epeirae first spin an auxiliary intended to strengthen the stays.  This spiral, formed of plain, non-glutinous thread, starts from the centre and winds in rapidly-widening circles to the circumference.  It is merely a temporary construction, whereof naught but the central part survives when the Spider has set its limy meshes.  The second spiral, the essential part of the snare, proceeds, on the contrary, in serried coils from the circumference to the centre and is composed entirely of viscous cross-threads.

Here we have, following one after the other merely by a sudden alteration of the machine, two volutes of an entirely different order as regards direction, the number of whorls and intersection.  Both of them are logarithmic spirals.  I see no mechanism of the legs, be they long or short, that can account for this alteration.

Can it then be a premeditated design on the part of the Epeira?  Can there be calculation, measurement of angles, gauging of the parallel by means of the eye or otherwise?  I am inclined to think that there is none of all this, or at least nothing but an innate propensity, whose effects the animal is no more able to control than the flower is able to control the arrangement of its verticils.  The Epeira practises higher geometry without knowing or caring.  The thing works of itself and takes its impetus from an instinct imposed upon creation from the start.

The stone thrown by the hand returns to earth describing a certain curve; the dead leaf torn and wafted away by a breath of wind makes its journey from the tree to the ground with a similar curve.  On neither the one side nor the other is there any action by the moving body to regulate the fall; nevertheless, the descent takes place according to a scientific trajectory, the ‘parabola,’ of which the section of a cone by a plane furnished the prototype to the geometer’s speculations.  A figure, which was at first but a tentative glimpse, becomes a reality by the fall of a pebble out of the vertical.