REPORT ON THE RADIOLARIA. li 



CHAPTER III THE EXTRACAPSULUM. 



( 81-100). 



81. The Components of the Extracapsulum. The extracapsulum or extracapsular 

 malacoma, under which name are included all those parts of the soft body which lie 

 outside the central capsule, consists of the following constant and important constituents : 



(l) The calymma or extracapsular jelly -veil ; (2) the sarcomatrix or layer of exoplasm 

 immediately surrounding the membrane of the central capsule ; (3) the sarcodictyum or 

 network of exoplasm, covering the surface of the calymma ; (4) the pseudopodia or 

 radial fibres of exoplasm, which may again be subdivided into intracalymmar pseudo- 

 podia, uniting the sarcomatrix and sarcodictyum, and extracalymmar pseudopodia, 

 radiating freely into the water outside the calymma. 



82. TJie Calymma. The calymma or extracapsular jelly-veil of the Radiolaria is 

 always the most voluminous portion of the extracapsulum, and in spite of its simple 

 structureless constitution is of great morphological and physiological importance. In 

 all Radiolaria this gelatinous mantle completely surrounds the central capsule,, but is 

 separated from its outer surface by a continuous, though thin, layer of exoplasm, the 

 sarcomatrix. The pseudopodia radiating from the latter pierce the calymma, form the 

 sarcodictyum at its surface, and radiate from its nodal points freely into the surrounding 

 water. The calymma is rarely visible in living freshly captured Radiolaria, examined 

 in sea-water, for its gelatinous substance is perfectly hyaline, colourless and pellucid, 

 and possesses the same refractive index as sea-water ; but when the object is removed 

 from this fluid and transferred to carmine solution or some other colouring matter, the 

 extent and figure of the calymma become apparent, for the staining fluid does not at 

 first penetrate into the gelatinous material. When this has taken place, however (after 

 a longer or shorter time), and the gelatinous material has become coloured, its form and 

 size may be observed by the converse experiment ; the object is transferred once more 

 to water and the outlines of the calymma become as clear as those of the central capsule. 

 The same is the case with dead specimens in which the sticky surface of the calymma 

 has become covered with dust. 



The jelly-veil of the Radiolaria was recognised even by the earliest observers of the group, 

 Meyen (1834), and Huxley (1851), and compared with that of the Palmellaria ; the former noticed 

 it in Physematium and Sphcerozoum (L. N. 1, p. 283), and the latter in Thalassicolla and Collosphcera 

 (L. N. 5, p. 433). In all these SPUMELLARIA, both in the monozootic Tlialassicolla and in the poly- 

 zootic Sphcerozoum and Collosphcera, the calymma is very voluminous and filled with large alveoli. 

 Meyen called them " muco-gelatinous masses, in the interior of which are contained small equal-sized 

 vesicles"; Huxley likewise found clear vesicles in the jelly and compared them with Dujardin's 

 vacuoles. Johannes Miiller observed the jelly-veil in many different Radiolaria, in particular in 

 the Acanthometra, first discovered by him, but erroneously believed that it only originated 



