Page:The aquarium - an unveiling of the wonders of the deep sea.djvu/220

Rh can look at the sight I am speaking of, without feeling certain that the optical process is one of concave reflection and convergence of the rays; and that the reflecting surface is in the interior of the globose compound eye. The reflection is seen whatever part of the eye is opposite the light, (provided it be facetted of course) but is most full direct in front, where no unfacetted portion can be seen. Yet it certainly has no connexion whatever with reflection from the exterior surface, as might be suggested by any one who has not actually seen it: the effect of this would be a minute point of light, very different from this broad round gleam.

The different species of Pagurus, and Crabs, as Portunus, exhibit the same phenomenon, but in a lower degree; the disk of light being smaller and of less brilliance; though their eyes are larger. I have seen the same appearance in the eyes of Moths and other nocturnal insects; so that doubtless it is dependent on the common structure of facetted compound eyes.

It is pretty to see the Prawn fed. When a morsel of food is dropped through the water near its head, the excessively long antennæ, (especially the long filaments of the superior pair, which are carried perpendicularly upwards) seem principally to take cognizance of its presence and of its qualities. The eyes, though evidently alert, are I think less trusted. As the morsel comes within reach, the second feet, the principal organs of prehension, are stretched out, with the two fingers (pincers) widely extended; these seize it with the most easy action possible, and in a moment thrust it towards the mouth.