as in unorganised nature; unless it is evident that the maintenance of the species depends upon it. But this is the case with many plants whose fructification only takes place by means of insects, which either bear the pollen to the stigma or bend the stamina to the pistil. The common barberry, many kinds of iris, and _Aristolochia Clematitis_ cannot fructify themselves at all without the help of insects (_Chr. Cour._ Sprengel, _Entdecktes Geheimniss, &c._, 1793; Wildenow, _Grundriss der Kräuterkunde_, 353). Very many diœcia, monœcia, and polygamia are in the same position. The reciprocal support which the plant and the insect worlds receive from each other will be found admirably described in Burdach’s large Physiology, vol. i. § 263. He very beautifully adds: “This is no mechanical assistance, no make‐shift, as if nature had made the plants yesterday, and had committed an error which she tries to correct to‐day through the insect; it is rather a deep‐lying sympathy between the plant and the animal worlds. It ought to reveal the identity of the two. Both, children of one mother, ought to subsist with each other and through each other.” And further on: “But the organised world stands in such a sympathy with the unorganised world also,” &c. A proof of this _consensus naturæ_ is also afforded by the observation communicated in the second volume of the “Introduction into Entomology” by Kirby and Spence, that the insect eggs that pass the winter attached to the twigs of the trees, which serve as nourishment for their larvæ, are hatched exactly at the time at which the twig buds; thus, for example, the aphis of the birch a month earlier than that of the ash. Similarly, that the insects of perennial plants pass the winter upon these as eggs; but those of mere annuals, since they cannot do this, in the state of pupæ.