LATTICE WORKERS, OR POLYCYSTINA. 103 



protection of the Radiolaria. The production of the 

 light depends, probably, as in other phosphorescent 

 organisms, upon the slow oxidation of the fat 

 globules, which combine with active oxygen in the 

 presence of alkalis." 



As to sensation in the Radiolaria, it must be ad- 

 mitted to be in an inferior degree of development. 

 For although subject to various stimuli, and possess- 

 ing a certain power of discrimination, no special 

 sensory organs are differentiated ; the pseudopodia 

 acting both as organs of motion and sensation. In 

 general they seem to be sensitive to pressure, to 

 temperature, to light, and to the chemical compo- 

 sition of the sea-water. The reaction, subject to 

 these stimuli, correspond to the sensation of pleasure, 

 or dislike, which they elicit, in the motion of the 

 protoplasm, changes in the currents, and in contrac- 

 tion of the central capsule and the pseudopodia. 

 Professor Haeckel considers that the central capsule 

 contains the common central vital principle, which 

 he terms the " cell-soul," and that it may be regarded 

 as a simple ganglion cell, comparable to the nervous 

 centre of the higher animals, whilst the pseudopodia 

 are analogous to a peripheral nervous system. 



Only a few words are requisite on the distribution 

 of these organisms, since they are found in seas all 

 over the world, under all climatic conditions, and all 

 depths. To say as much as this is to recognise them 



