. The biology of marine animals. Marine animals; Physiology, Comparative. 546 THE BIOLOGY OF MARINE ANIMALS of the light-cell. Triopa fulgwans, Kaioplocamus ramosum and Plocamo- phorus ocellatus are other luminescent nudibranchs. A myopsid squid Heteroteuthis dispar from deep water in the Mediter- ranean emits a luminous cloud when disturbed, comparable to the dis- charge of ink by shallow-water species. Although this has been considered another instance of symbiotic bacteria, it is probable that the luminescent secretion is produced by the animal. The luminous organ is a rather large gland pa
. The biology of marine animals. Marine animals; Physiology, Comparative. 546 THE BIOLOGY OF MARINE ANIMALS of the light-cell. Triopa fulgwans, Kaioplocamus ramosum and Plocamo- phorus ocellatus are other luminescent nudibranchs. A myopsid squid Heteroteuthis dispar from deep water in the Mediter- ranean emits a luminous cloud when disturbed, comparable to the dis- charge of ink by shallow-water species. Although this has been considered another instance of symbiotic bacteria, it is probable that the luminescent secretion is produced by the animal. The luminous organ is a rather large gland partially surrounded by the ink sac. It possesses a reservoir and opens into the mantle cavity by two apertures. The gland is lined with low epithelial cells, and is provided with muscles for squeezing out the Photocytes^ Nerve Fig. Light-producing Glandular Cells of the Gastropod Phyllirrhoe bucephala A nerve is shown terminating on the photocyte to the right. (After Dahlgren, 1916.) A similar light gland is present in the Japanese squid Sepiolina nipponensis {26a). Among the lower chordates various balanoglossids emit a luminous slime from the whole surface of the body. Light-producing species include Balanoglossus minutus and Ptychodera bahamensis. Extracellular luminesc- ence has also been described in fish, but some of the species which dis- charge a luminous secretion appear to harbour symbiotic bacteria, Malacocephalus. Beebe and Crane (3) noticed a mucous luminescent coat- ing adhering to the teeth of the bathypelagic angler-fish Linophryne arcturi, and the deep-water eel Saccopharynx harrisoni has a pair of troughs along its back which are filled with a bluish-white luminous substance. Many of the deep-water anglers (Pediculati) are provided with a luminescent lure (illicium) representing a modified first dorsal fin ray (Fig. ). The escal light-organ at the tip of the illicium has a transparent window through which the light can shine and conta
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