A. EARLAND ON KADIOLARIA. lit 



directions woiikl also tend to act against gravity by increasing 

 the frictional resistance. 



Radiolaria are able to creep slowly along the surface of any 

 solid body with which they may be in contact by contraction of 

 the pseudopodia, but this means of locomotion can only be of 

 service when they are in actual contact with the sea bottom, 

 which probably is of rare occurrence during life. Beyond this 

 their power of motion seems to be limited to rising or sinking 

 vertically in the water. This is probably managed by means 

 of contraction or expansion of the calymma by osmosis, which 

 would affect the specific gravity of the organism. It is also 

 possible that the protrusion or retraction of the pseudopodia 

 may effect the same result. Brandt considers that the sinking 

 and rising of the Radiolaria are associated with the disappear- 

 ance and reappearance of vacuoles. 



Phosphorescence is widely distributed among the Radiolaria. 

 They emit a greenish or yellowish light, which appears to radiate 

 from the fat globules within the central capsule, and is probably 

 due to the slow oxidation of the fat globules. It doubtless 

 serves as a warning light for the protection of the Radiolaria, as 

 phosphorescent animals are generally armed with spines, stinging 

 cells or other defensive weapons. 



The Radiolaria have no specially differentiated sense organs, 

 although the pseudopodia perhaps act as organs of sensation 

 as well as of motion. They have been proved to be sensitive to 

 the stimuli of pressure, temperature, light, and variations in 

 the chemical composition of the water in which they are 

 suspended. 



Distribution. 



The Radiolaria are wholly marine, and have a world-wide 

 distribution, from the Equator to the highest latitudes yet 

 reached. In many parts of tha world they occur in astonishingly 

 large masses, both on the surface, in different zones of depth, and 

 near the bottom. They must play a most important part in 

 the economy of marine life, especially as food for other animals. 

 As with other forms of life, the greatest development of species 

 occurs in the tropics, while in high latitudes we find relatively 

 few species, but these occurring in prodigious numbers. This 



