Swammerdam and Cuvier the recurrent nerve. The double nervous web preponderates in the Orthoptera, and especially in Locusta and Gryllus.
The remarkable and characteristic attribute of this system is, that it is in no degree influenced by the changes which the ventral system undergoes in the different stages of metamorphosis. It is quite as fully developed in the young larva as in the perfect insect and vice versa. It may be thence naturally inferred that its functional uses are required at the earliest stage of life; and this in reality is the case, for it is destined to preside over the functions of what has been called vegetative life, which reach their highest pitch of activity in larvæ.
As the nerves constitute the fundamental organs of all sensation, this is the proper place to speak of the senses, the avenues through which the properties of external objects are conveyed to them. Judging partly from their structure, and partly from the actions that follow certain impressions received from without, we are inevitably led to infer, that insects possess at least all the senses which exist in the higher animals, some of them even in a greater state of perfection. Nay, it is by no means improbable that additional ones have been assigned them, to which we have nothing analogous in our own system, and of which, therefore, we cannot form any accurate conception. It is even a matter of doubt what organs are to be regarded as the seat of certain senses, the existence of which we are scarcely authorised to call in question.
