. Fig. 7. Nebaliella extrema. A. Side view of rostrum, eyes, antennules and antennae, the right half of the carapace having been partly cut away. B. Oblique front view of eyes and rostrum. ant. I, antennule; ant. 2, antenna; e. eye; eye muscle;/.r. flange of rostnun; hook on second joint of antenna; heel of eye; knob above antennule; keel of rostrum. stricted by the posterior heel. From the lateral view in Fig. 7 A, it will be seen that this heel is lodged in a gap between the antennulary knob and the antennule itself. Contrac- tion of the eye muscle can, therefore, on
. Fig. 7. Nebaliella extrema. A. Side view of rostrum, eyes, antennules and antennae, the right half of the carapace having been partly cut away. B. Oblique front view of eyes and rostrum. ant. I, antennule; ant. 2, antenna; e. eye; eye muscle;/.r. flange of rostnun; hook on second joint of antenna; heel of eye; knob above antennule; keel of rostrum. stricted by the posterior heel. From the lateral view in Fig. 7 A, it will be seen that this heel is lodged in a gap between the antennulary knob and the antennule itself. Contrac- tion of the eye muscle can, therefore, only have one action. It must cause the eye to pivot about this point. This will make the anterior margins of the eyes rotate inwards towards the middle line. Now the eyes form the lateral margins of the anterior entrance to the filter chamber—the only entrance by which food-bearing water is sucked in— and their rotation inwards will diminish the size of this entrance. There is thus in the eyes a mechanism by which the amount of water, and hence the amount of food, en- tering the carapace can be controlled.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectscientificexpedition
