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, e.g. 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 Sea. 



