RADIOLARIA. 877 



there are several globules for the most part numerous and peripheral. They 

 are highly refractile, usually colourless, but may be yellow, brown, red, blue ; 

 and in the Spumellaria, especially the colonial, with a laminated organic 

 substratum, not albuminous according to Brandt. Pigment, red, yellow, 

 brown, rarely violet or blue, still more rarely green, is present as minute 

 granules. Crystalloids, usually known as crystals, are of two kinds 



(1) small, more or less like a whetstone, destined to be inclosed as reserve 

 material one in each spore, not observed in Nassellaria or Phaeodaria ; 



(2) large, apparently of an excretory nature, and indestructible by a red 

 heat, present only in some colonial Collosphaerida, side by side with the 

 small. Both kinds are formed only when sporulation is about to take 

 place, as is the blue pigment of Collosphaera Huxleyi and Myxosphaera 

 coeridea. Masses of crystals (? excretory) occur in the vacuoles of Thalassi- 

 collida and some Phaeodaria. Laminated circular or elliptical concretions 

 of unknown nature are found in some Spumellaria and Nassellaria ; violin- 

 shaped and highly refractile bodies in the same two groups and some 

 Acantharia. The nucleus is at first single, but in the colonial Spumellaria 

 and very many Acantharia, it undergoes division into many nuclei at an 

 early period. The single nucleus is central and often of large size, 

 e. g. 1-2 mm. in some large Thalassicollida ; in most Phaeodaria it 

 attains -f-f of the diameter of the central capsule. Its shape is typically 

 spherical, but varies concomitantly with that of the capsule ; it is sometimes 

 irregular and occasionally has radial claviform processes (Thalassophysa, 

 Thalassophila). It may inclose by growth one or more of the inner shells 

 when the shell is multiple. The small nuclei of the colonial Spumellaria 

 are homogeneous, but in the Acantharia they may be nucleolate. The 

 single nucleus has a distinct membrane, thick, double contoured, and in 

 Thalassicollida probably porous. It is more or less homogeneous, and 

 may possess nucleoli (some Spumellaria, the Nassellaria and Phaeodaria}. 

 A chromatin network with nucleolar enlargements has been demonstrated 

 in Thalassicolla coerulea. 



The extracapsular portion of the body consists of a gelatinous 

 skeleton or calymna, and protoplasm with various inclosures. It has been 

 shown experimentally on Thalassicolla nucleata that it can be regenerated 

 from the central capsule if the latter be removed artificially. The calymna 

 is separated from the central capsule by the sarcomatrix (infra). It is 

 hyaline, rarely opalescent, of the same degree of refrangibility as sea-water, 

 structureless but occasionally laminated, of a soft consistence in the young 

 form, but varying in the adult, where it is sometimes as firm as cartilage. 

 It grows during life, and is greatly developed in the Spumellarian Collo- 

 daria. It resembles the skeleton in shape, and in Nassellaria and Phaeo- 

 daria usually incloses it completely. In the Acantharia a regularly 

 polygonal network of fibres is disposed superficially between the calymnal 



