60 CRUSTACEA——-COPEPODA CHAP. 
Heterochaeta papuligera, Oncaea conifera is also phosphorescent. 
It is often stated that Sapphirina (p. 69) is phosphorescent, but 
its wonderful iridescent blue colour is purely due to interference 
if 
Fic. 27.—Dorsal view of Anomalo- 
cera pattersoni, 6, x 20. (After 
Sars. ) 
colours, and has nothing to do with 
phosphorescence. Giesbrecht has 
observed that the phosphorescence 
is due to a substance secreted in 
special skin-glands, which is jerked 
into the water, and on coming into 
contact with it emits a phosphor- 
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 Gniesbrecht 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- 
cera pattersoni (Fig. 27) is one of the commonest elements 
in the plankton of the North Sea. 
