THE RADIOLARIA 115 



manent excretion, but is composed of a substance capable of 

 adaptation, by growth or dissolution, to changes in the endoplasm. 



The walls of this structure are perforated by fine pseudopodia 

 that connect the endoplasm with the exterior in the manner 

 severally characteristic of the Peripylaria, Monopylaria, and 

 Tripylaria (pp. 102-9). 



The evenly distributed or segregated pores of the first group 

 admit not only fine plasmic connections, but in Acantharia they 

 also transmit axopodia and radial spicules. 



The single pore-plate of the Monopylaria, which, according to 



FIG. 10. 



Cytodadus spinosu*. x 10. (After Schroder [38].) One of the Peripylaria, to show the 

 branched central capsule (C.c), the radiate single spicule (Sp), and the voluminous ectoplasm 

 supported by the spicular rays. It has been recently found off the coast of Japan. 



Hertwig, consists of perforated, thickened rods of capsular mem- 

 brane, is not thoroughly understood. In most Nassellaria the 

 pores are, of course, confined to one plate-like extremity of the 

 -capsule, but they may be evenly distributed over the basal plate, 

 confined to a peripheral zone, OF to three circles, which in Tridictyopus 

 project peripherally. Associated with this pore-plate is a peculiar, 

 -cone-like, fibrillated structure which projects inwards towards the 

 nucleus (Fig. 5, B, p). According to Hertwig this cone is an 

 invagination of the capsular membrane, and the fibrillae are con- 

 tinuations of those that pass through the pore-plate, on their way 

 to join the endoplasm at the apex of the cone. Biitschli, however, 



