102 TOILERS IN THE SEA. 



The movement of the swarm-spores by the oscilla- 

 tion of the thread, or flagellum, does not differ 

 essentially from that of ordinary flagellate infusoria. 

 The swimming of mature Radiolaria is confined to a 

 vertical direction, causing the rising or sinking in the 

 water. This is probably due to increase or diminu- 

 tion of the specific gravity, which is perhaps brought 

 about by the retraction or protrusion of the pseudo- 

 podia. The most important organ, however, is 

 probably the jelly- veil, by the contraction of which 

 the specific gravity is increased, while it is diminished 

 by its expansion. The slow creeping locomotion 

 only occurs when the animal comes in contact with a 

 solid surface, and is possibly due to muscle-like con- 

 tractions of the pseudopodia. 



On the subject of phosphorescence in the Radio- 

 laria, Professor Haeckel remarks that " many Radio- 

 larians shine in the dark, and their phosphorescence 

 presents the same phenomena as that of other 

 luminous marine organisms ; it is increased by 

 mechanical and chemical irritation, or renewed if 

 .already extinguished. The light is sometimes 

 greenish, sometimes yellowish, and appears generally 

 (if not always) to radiate from the fatty sphseres of 

 the inner capsule. Thus these latter unite several 

 functions, inasmuch as they serve, firstly, as reserve 

 stores of nutriment, secondly, as hydrostatic ap- 

 paratus, and thirdly, as luminous organs for the 



