322 BIOLOGY OF THE PROTOZOA 



membrane of organic substance, presumably chitin or pseudo- 

 chitin, between tlie zones of ectoplasm and endoplasm of a heliozoon 

 like Aciinosphcerium. Such a meni'brane is present in Radiolaria 

 and is called the "central capsule." It separates the intracapsular 

 protoplasm (endoplasm) from the extracapsular protoplasm (ecto- 

 plasm). Minute openings, the pylea, through which communica- 

 tion between the two main zones of protoplasm is possible, are 

 uniformly distributed, or arranged in lines and patterns, or limited 

 in number at definite polar positions. These serve as a basis of 

 classification for the main subdivisions of the group according to 

 the scheme early adopted by Hertwig. 



The intracapsular protoplasm contains nuclei, fat particles and 

 plastids of one kind or another, and as Verworn showed, it can live 

 independently of the ectoplasm for a time but ultimately regenerates 

 it. The outer or extracapsular plasm is composed of four parts 

 according to Haeckel. The outermost part is a zone of pseudo- 

 podia which originate, however, in the more deeply lying fourth 

 zone and then ex-tend through the gelatinous ectoplasm to the per- 

 iphery. A second zone— sarcodictyum— is in the form of a mesh- 

 work which extends through the third zone of gelatinous material 

 termed the calymma which forms the greater bulk of the ecto- 

 plasm. A fourth and most important zone, the sarcomatrix lies 

 close against the central capsule and is the go-between for the intra- 

 and extracapsular portions. The sarcomatrix is also the seat of 

 digestion 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. Hertwig (1879) 

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

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

 perforated by pores arranged regularly around the entire surface; 

 (2) Actipylea, in which the pores are arranged in groups or lines 

 over the surface; (.3) Monopylea, in which there is only one such 

 group of pores. In these forms the perforated disc is connected 

 with the center of the central capsule by a conical mass of endoplasm, 

 the podoconus, rich in food particles and granules (Fig. 151 p. 343) ; 

 (4) Cannopylea, in which the membrane aroinid the pores is drawn 

 out into funnel-like projections termed astropyles of which one is 

 the primary, the other two secondary. In these forms furthermore, 

 the central capsule is double. Haeckel found that certain types of 

 skeleton are characteristic of the difterent types of membrane per- 

 foration and gave corresponding names to the four legions of 

 Hertwig, viz.: (1) SpumeUaria, or practically naked forms; (2) 

 Acantharia, with spicules and bars supposed to be of horn or acan- 



