THE NATURALIST.

Otago Witness, Issue 1880, 2 December 1887, Page 36

THE NATURALIST.

Hundred-eyed Animals and What They See. If the lobster's eye consists of more than a hundred separate eyelets, each with its own lens, what sort of a picture of the outward world does the animal see ? Does he see a hundred different images of the same object 7 As he crawls along the rocky sea bottom in congenial haunts, where the wily fishermen tempt his epicurean appetite with his favourite food, does he see a hundred lobster pots where there is only one 1 Does the single whelk-bait within look like a hundred tempting morsels? The' same question would apply to the lobster's enemies, great fishes, with flat, pavementlike teeth, which easily crush through the armour-plates which form his^shell. Supposing the lobster to multiply such enemies visually by the hundred, his life could scarcely be said to be a happy one. ' The question thus raised is an interesting one, especially as it applies not only to lobsters, but also to all insects. For instance, does the housefly, with its 4000 eyeleta, see 4000 . housemaids dusting the window pan© when there is really only one ? Does the cabbage butterfly, with its 17,000 eyelets, see every cabbage multiplied 17,000 times ? And does the dragonfly in the same way see 36,000 turquoise - coloured companions hawking about by the pond side when there is only one ? The problem has been fought over by zoologists with much vigour until quite recently. The advocates of the multiple vision theory, astonishing as that theory may seem, have not been wanting ; but eventually the advocates of the single vision theory are now in possession of the wellfought field. Whatever be tho number of eyelets, or the number of pictures received on the cornea, it is the retina which receives the ultimate impression from external objects, The delicate, subtle, and mysterious nerve ends which we call the retina are the ultimate sensory apparatus which determines what shall be seen. The conclusion arrived at is briefly this : Apart from the lenses and cones in front, the lobster's or insect's eye is a hollow sphere pierced by numerous closeset perforations, running down the facets towards the centre of the sphere. Only those rays can reach the retina which run in the axis of the perforation. Other rays than the axial rays are required to produce a complete picture at the retinal end of each perforation. It follows that the light-impres-sions caused by the axial rays, whoso number corresponds with the separate nerve rods, form a single picture or " mosaic " of points of sight on tho retina. — Leisure Hour.

Ants in the Channel Islands.— For some time past immense clouds of ants have been observed in the higher parishes of the island of Guernsey, and at the island of Sark. In Guernsey they have appeared in such numbers as to quite darken the air. The insects are feeble on the wing and are swept by millions into the sea when the breeze is blowing in that direction.

A Prize Wasp's Nest.— At Maiden-Er-leigh a wasp's nest, after having been smoked with sulphur, was recently dug oufc from a stack of turf. This nest measured the extraordinary size of 30in in circumference, and contained thousands of wasps ! Its discovery was opportune, for a prize had been offered for the finest wasp's nest, at the Cottage Garden Exhibition in the neighbourhood, and this nest took the prize without any difficulty.

Bruma.— Naturalists tell us that birds do build their nests according to the character of the season that is coming. If it is to be rainy, they build in a sheltered position ; if windy, they thatch straw and leaves on the inside of the nest, between the twigs and the lining; if very windy, they take extra care to bind their nest firmly to the bough with pliant twigs. But if the season promises to be a fair and pleasant one, they build in an open position, without taking any of these special precautions.