THE RADIOLARIA 



137 



through the oral aperture and develops into a new individual 

 (Borgert [2 la], p. 100). 



The most remarkable case of multiple fission occurs in the 

 Thalassophysidae, and constitutes the only known means of increase 



FIG. 20. 



Illustrating fission in the Acanthometrida. (After Popowsky.) A, Acanthometron bifidum, 

 about to divide. The spicules are arranged in two bundles. The central capsule has dis- 

 appeared. The ectoplasm is a mere hyaline border round the granular endoplasm, x!50. 

 B, fission of Amphilonche atlantica. My, the myonemes, x 150. C, regeneration of the same ; 

 formation of a directive large spicule, x!50. D, spicules reassuming their characteristic 

 arrangement, x!50. 



in this family. Fig. 21 illustrates the process, which has been 

 investigated by Brandt (25). The central capsule and nucleus 

 become irregular -branching, vermicular, or radiating structures. 

 The oil-globules and their associated pigment granules become dis- 

 seminated through the endoplasm. Then the nucleoplasm breaks 

 up into a vast number of minute homogeneous corpuscles, followed 



