RADIOLARIA 



ing into yellow or brown, though violet, blue, and green also 

 occur. The " phaeodium," ^ however, that gives its name to the 

 Phaeodaria, is an aggregate of dark grey, green, or brown granules 

 which are probably formed in the endoplasm, but accumulate in 

 the extracapsular plasm of the oral side of the central capsule. 

 Inorganic concretions and crystals are also found in the contents 

 of the central capsule, as well as aggregates of unknown com- 

 position, resembling starch-grains in structure. 



In the Monopylaea, or Nassellaria (Figs. 25, B, 26, A), the 

 endoplasm is differentiated above the perforated area of the 

 central capsule into a cone of radiating filaments termed the 

 " porocone," which may be channels for the communication 

 between the exoplasm and the endoplasm, or perhaps serve, as 

 Haeckel suggests, to raise, by their contraction, the perforated 

 area : he compares them to the myophane striae of Infusoria. 

 In the Phaeodaria (Fig. 26, B), a radiating laminated cone is 

 seen in the outermost layer of the endoplasm above the principal 

 opening (" astropyle "), and a fibrillar one around the two accessory 

 ones (" parapyles ") ; and in some cases, continuous with these, the 

 whole outer layer of the endoplasm shows a meridional striation. 



The nucleus is contained in the endoplasm, and is always at 

 first single, though it may divide again and again. The nuclear 

 wall is a firm membrane, sometimes finely porous. If there are 

 concentric shells it at first occupies the innermost, which it may 

 actually come to enclose, protruding lobes which grow through 

 the several perforations of the lattice -work, finally coalescing 

 outside completely, so as to show no signs of the joins. In the 

 Nassellaria a similar process usually results in the formation of 

 a lobed nucleus, contained in an equally lobed central capsule. 

 The chromatin of the nucleus may be concentrated into a central 

 mass, or distributed into several " nucleoli," or it may assume 

 the form of a twisted, gut-like filament, or, again, the nuclear 

 plasm may be reticulated, with the chromatin deposited at the 

 nodes of the network. 



The skeleton of this group varies, as shown in our conspectus, 



1 The pigment is singularly resistant and insoluble, and shows no proteid 

 reaction. Borgert states that it appears to he formed in the oral part of the endo- 

 plasm, and to pass through the astropyle into the ectoplasm, where it accumulates. 

 It is probably a product of excretion, and may serve, by its retention, indirectly to 

 augment the surface. See Borgert, " Ueb. die Fortpflanzung der tripyleen Eadio- 

 larien " in Zool. JccJiri. .Anal. xiv. 1900, p. 203. 



VOL. I ^ 



