RADIOLARIA 



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from others in form and structure. The majority of this group 

 possess 20 rods radiating from the center. The rod-shaped skele- 

 tons emerge from the body in most cases along five circles, which 

 are comparable to the equatorial, two tropical and two circum- 

 polar circles of the globe, which arrangement is known as M tiller's 

 law, since J. M tiller first noticed it in 1858. 



The life-cycle of the Radiolaria is very incompletely known 

 (Fig. 167). Binary or multiple fission or budding has been seen 

 in some Peripylea, Actipylea, and Tripylea. Multiple division is 



Fig. 167. Diagram illustrating the life-cycle of Actipylea (Kiihn). 

 a, mature individual; b, c, binary fission; d, e, multiplication by bud- 

 ding; f, mature individual similar to a; g, formation of swarmers; 

 h-j, supposed, but not observed, gametogony of two swarmers pro- 

 ducing a zygote; k, 1, young individuals. 



