Berœ

Berœ, one of the commonest representatives of the most intensely active sub-class of Cœlenterates—the Ctenophora (q.v.). These are free-swimming pelagic animals, of great delicacy and beauty, generally of a more or less cylindrical form, and without any trace of skeleton, which indeed rarely occurs in the more active lower animals. Berœ is the type of a small family, Beroidæ, in which the body is oval or spherical, but slightly flattened in one plane. They are transparent, and often beautifully coloured, especially during reproductive periods. The lower pole is occupied by the large mouth, which leads into a spacious and complex alimentary canal ending at the top. The superior pole bears a complex sensory organ, and between the two are eight meridian bands, each bearing a row of comb-like plates formed from the union of cilia. These ciliary plates move very rapidly, producing a beautiful iridescence, and wafting the berœ through the water in any desired direction. It has been recently shown that the limy 'otocyst,' which forms part of the sense organ, may act as an automatic balancing and steering apparatus. Like many other active marine animals, the Ctenophora are phosphorescent, and berœ is one of the most brilliant examples. The light shines out especially from the regions of the meridional bands. The berœs are very voracious, feeding on small crustaceans and the like, but with a marked preference for their own relatives. They are themselves swallowed in shoals by whales. During the day they descend to deeper water, but come to the surface at night. In autumn they seem to frequent the surface more constantly, and may then be observed in great crowds. The distribution of the genus, which includes three certain species, is very wide, and one form is quite common on British coasts. Berœ differs most markedly from related forms, such as Cydippe, Pleurobrachia, &c., in the absence of a pair of long tentacles. See CTENOPHORA.