MORPHOLOGY AND TAXONOMY OF THE SARCODINA 4^9 



then extend through the gelatinous ectoplasm to the periphery. 

 A second zone — sarcodictyum — is in the form of a meshwork 

 which extends through the third zone of gelatinous material termed 

 the calymma which forms the greater bulk of the ectoplasm. A 

 fourth and most important zone, the sarcomatrix, lies close against 

 the central capsule and is the go-between for the intra- and extra- 

 capsular portions. The sarcomatrix is also the scat of digestion 



Fig. 181.— Radiolarian central capsules. A, Thalassolampe, type of peripylea; 

 B, Acanthometron, type of actipylea; C, Aulographis, type of tripylea; I), Triptero- 

 calpis, type of monopylea ; c, central capsule: n, nucleus. (From Calkins after 

 Haeckel.) 



and assimilation, the food coming to it by way of the pseudopodia 

 and the network of the sarcodictyum. 



As the means of communication between the central protoplasm 

 and the sarcomatrix is of vital importance to the organism, the 

 arrangement of the apertures in the central capsule offers a good 

 character for the classification of the Radiolaria. Ilertwig (1879) 

 who first used this feature, divided the group into four legions as 

 follows: (1) Peripylea, in which the membrane of the capsule is 



