xl THE VOYAGE OF H.M.S. CHALLENGER. 



from twenty to fifty roundish or spherical, strongly refracting nucleoli, are present ; more 

 rarely there are several hundred very small ones. Sometimes the nucleus is penetrated 

 by fine trabeculae, in whose meshes lie the nucleoli (PI. 101, fig. 2). In certain nuclei, 

 which contained a few large nucleoli, these were of irregular form, probably the result of 

 amoeboid movements (PI. 101, fig. 1). In the formation of spores in the CANNOPYLEA, the 

 nucleus apparently becomes dissolved, and its numerous nucleoli develop directly into 

 the nuclei or mother-nuclei, which produce the nuclei of the flagellate spores. Further- 

 more, many PHJEODARIA seem to multiply by simple cell-division, since very commonly 

 (especially in the Phseocystina and Phseoconchia) two large nuclei (right and 

 left), may be met with in one central capsule ; sometimes also a single large nucleus, in 

 which a sagittal constriction marks the commencing division of the capsule (PL 101, figs. 

 2, 36; PI. 104, fig. 3; PL 124, fig. 6, &c.). 



The large nucleus of the PH^EODAEIA was first described in my Monograph in 1862, in the case 

 of Aulaeantha (p. 263), Aulosphcera (p. 359), and Ccelodendrum (p. 361), as a " large, spherical, thin- 

 walled endocyst," from O'l to 0'2 mm. in diameter. More detailed descriptions, especially with 

 respect to the behaviour of the nucleoli were given by E. Hertwig in 1879 (L. N. 33, p. 97). 



71. The Endoplasm or Intracapsular Protoplasm. In all Radiolaria the intracapsular 

 protoplasm, which, for the sake of brevity, may be termed " endoplasm," constitutes 

 originally, and especially in the earliest stages, the only important content of the central 

 capsule, except the nucleus. In certain SPUMELLARIA and NASSELLARIA, of simple 

 structure and of small dimensions, this condition persists for a long period, and the 

 endoplasm then appears as a homogeneous, colourless, turbid or finely granular, mucous, 

 semi-solid mass, which cannot be distinguished from the ordinary undifferentiated proto- 

 plasm of young cells ; no definite structure, and in particular, no fibrillar network, can 

 be discovered in it even by the use of the customary reagents. In the great majority of 

 the Radiolaria, however, this primitive homogeneous condition of the endoplasm is very 

 transient, and it soon undergoes definite modifications, becoming differentiated into 

 separate parts or producing new constituent contents. Such products of the internal 

 protoplasm are in particular hyaline spheres (vacuoles and alveoles), oil-globules, pigment- 

 bodies, crystals, &c. The most important of the differentiations which take place in 

 the endoplasm is that into an internal, granular, medullary substance and an external, 

 fibrillar, cortical substance ; although the various legions behave somewhat differently 

 in this respect ( 77-80). 



i 



72. Intracapsular Hyaline Spheres. The central capsule of very many Radiolaria 

 contains in its endoplasm numerous spherical bodies of varying size, which consist of 

 watery or albuminous fluid, and have previously been regarded as nuclei, or described as 

 products of the internal protoplasm, under various names, such as " spherical transparent 



