2G8 A. EARLAND ON RADIOLARIA. 



configuration of this protoplasmic network is very variable, and 

 as a rule is very irregular in form, though in some groups it 

 appears to retain a regular shape. In the Spongosphserida and 

 Spongodiscida, which form a spongy cortical skeleton, the proto- 

 plasm of the sarcoplegma becomes directly metamorphosed into 

 silex. From a physiological point of view the sarcoplegma is of 

 importance both for the nutrition and motion of the Radiolaria, 

 since it brings the sarcomatrix and the sarcodictyum with its 

 pseudopodia into direct connection. 



The Sarcodictyum. 



The sarcodictyum is a network of exoplasm forming a. 

 reticular covering on the outer surface of the gelatinous 

 calymma. It may be divided into a primary and a secondary 

 sarcodictyum. The original or primary sarcodictyum ramifies 

 over the surface of the primary calymma, and, like this, is of the 

 highest importance in the formation of the primary lattice shell. 

 If we regard the primary calymma as the foundation upon which 

 the lattice shell is deposited, then the primary sarcodictyum 

 fm-nishes the material from which it is developed. It may be 

 said that the primary lattice shell arises from a direct chemical 

 metamorphosis of the primary sarcodictyum, by a chemical 

 precipitation of the dissolved skeletal material which had been 

 stored up in the exoplasm. Hence the particular form of the 

 primary lattice sphere, with its regular or irregular meshes, is the 

 direct result of a corresponding form of the primary sarcodictyum. 

 The same is true of the secondary sarcodictyum, which ramifies 

 over the external surface of the calymma, and there forms the 

 secondary lattice shells, which retain the configuration of the 

 sarcode from which they have been precipitated. 



The Pseudopodia. 



The pseudopodia, as a rule, exhibit the same characteristic 

 features of these organs as in other Rhizopods. They are of two 

 kinds, myxopodia and axopodia. The former, which are found in 

 all Radiolaria, are usually long and thin flexible filaments of 

 sarcode radiating freely from the surface of the sarcodictyum 

 into the surrounding water, where they may branch or ana- 

 stomose to any extent. Granular movement may be observed 



