454 



DISTRIBUTION IN SPACE AND TIME 



among them are the Compound Jelly- Fishes (Siphonophora), 

 which are floating colonies, often of very complicated nature, as 

 the members of the colony are modified in many various ways in 

 order to fit them for diverse functions (see p. 103). 



Plankton Animalcules (Protozoa]. One very interesting form, 

 the Night-Light Animalcule (Noctiluca, fig. 1309), is a common 

 cause of the phosphorescent appearance of the sea around our 



Fig. 1311. Group of Foraminifera. i, Ammodiscus incertus; 2, A. charoides; 3, Trochammina coronata; 

 4, T. nitida; 5, Textularia agglutinans; 6, Verneuilina pygmaea; 7, Lagena seminuda; 8, jNodosaria scalaris; 

 9, Ramulina globulifera; 10, Polystomella imperatrix. 



coasts. Two groups are very dominant in the plankton, the 

 Ray- Animalcules (Radiolaria, fig. 1310) and the Forams (Fora- 

 mini/era, fig. 1311). The former possess a flinty skeleton, often 

 of great complexity and beauty, while the latter are provided 

 with elegant calcareous shells of the most various shapes. Vast 

 areas of the sea-floor are covered by soft " oozes", which are 

 largely composed of the hard parts of deceased members of 

 these two groups that are being continually rained down from 

 the surface waters. There also appear to be some few species 



