. The Cambridge natural history. Zoology. 6o CRUSTACEA COPEPODA HeterorJiaeta papilligera ; Oncaea conifera is also phosphorescent. It is often stated that Sap2:)]iirina (p. 69) is phosphorescent, bnt its wonderful iridescent blue colour is purely due to interference colours, and has nothing to do with phosphorescence. Giesbrecht has observed that the phosphorescence is due to a substance secreted in special skin-glands, wlaich is jerked into the water, and on coming into contact with it emits a pliosphor- escent glow. This substance can be dried up completely in a desiccated specimen and yet
. The Cambridge natural history. Zoology. 6o CRUSTACEA COPEPODA HeterorJiaeta papilligera ; Oncaea conifera is also phosphorescent. It is often stated that Sap2:)]iirina (p. 69) is phosphorescent, bnt its wonderful iridescent blue colour is purely due to interference colours, and has nothing to do with phosphorescence. Giesbrecht has observed that the phosphorescence is due to a substance secreted in special skin-glands, wlaich is jerked into the water, and on coming into contact with it emits a pliosphor- escent glow. This substance can be dried up completely in a desiccated specimen and yet preserve its phos- phorescent properties, the essential condition for the actual emission of light being contact with water. Similarly, specimens preserved in glycerine for a long period will phosphoresce when compressed in distilled water. From this last experiment Giesbrecht concludes that the phosphorescence can hardly be due to an oxidation process, but the nature of the chemical reaction remains obscure. Fam. 2. Candacidae. — This family comprises the single genus Candace, with numerous species distributed in the plankton of all seas. Some species, C. 'pectinata, Brady, have a practically world- wide distribution, this species being recorded from the Shetlands and from the Philippines. Fam. 3. Pontellidae.—This is a larger family also comprising widely distributed species found in the marine plankton. Anomalo- i one of the commonest elements. Fig. 27.—Dorsal view of Anomalo- .cera patlersoni, S , x 20. (After Sars.) cera pic^itersoni (Fig. 27) i in the plankton of the North Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harmer, S. F. (Sidney Frederic), Sir, 1862- ed; Shipley, A. E. (Arthur Everett), Sir, 1861-1927. ed. [London, Macmillan and Co. , Limited; New York, The Macmillan Compa
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