1530 THE VOYAGE OF H.M.S. CHALLENGER. 



the paraj^ylse often exhibit here, when observed from the face, a distinct radial striatiou 

 (compare Hertwig, loo. cit., p. 98, Ta£ x. figs. 6—14). Perhaps the radiate shape of 

 the operculum is only produced by radial folds of the endocapsa placed beyond it, and 

 these folds may be in turn the product of the radial fibrillse, which are prominent 

 beyond the astropyle. On the other hand, these fibrillae may be compared to the 

 muscular fibrillse or " myophane filaments " in the ectosarc of the Infusoria, and may 

 perhaps effect by their contraction a dilatation of the openings of the capsule. 



The nucleus of the PHiEODAHiA is always very large, usually about half or two-thirds 

 as broad as the central capsule, and placed either in its centre, or sometimes nearer to 

 one pole of the main axis, which is common to the capsule and its nucleus. Therefore 

 the diameter of the latter is usually half or even two-thirds of that of the capsule, and 

 may be in the majority 0"05 to 0'15, often 0'2 to 0'3, rarely more than 0'4 or less than 

 O'Ol mm. The form of the nucleus is rarely spherical, usually sjiheroidal, and it is 

 more depressed in the direction of the main axis than the capsule itself. In my 

 Monograph, where I gave the first description of it, I called it " Binnenblaschen." The 

 membrane of the vesicular nucleus is thin but rather firm, and contains a rather clear, 

 finely granulated substance, in which numerous nucleoli are usually scattered. (Compare 

 PL 101, figs. 1-10; PI. 102-104; PI. 123; PL 127, &c. ; the nucleus is marked by 

 n, the nucleoli by /.) 



The nucleoli are very different in respect to their form, size, number and arrange- 

 ment. Since these differences are very great even in different specimens of a single 

 species (as, e.g., in the common cosmopolitan Aulacantha scolymantha, Aulosphcera 

 trigonopa, Ccelodendrum ramosissimuin, &c.), it is probable that they represent 

 different stages of development and multiplication, and that the smallest fragments 

 of the nucleoli, or the final results of their repeated division, become the nuclei of the 

 flagellate spores, which are developed in the Ph^odaria just as in the other Radiolaria. 

 In the majority of nuclei examined, the number of the enclosed nucleoli proved to be 

 very great, fifty to eighty or more, often some hundreds, the greater their number the 

 smaller their size. Their form is usually irregular, roundish, or even amoeboid — 

 probably the result of amoebiform motions (PL 101, fig. 1). Sometimes the nucleoli were 

 regularly spherical, equidistant, and connected apparently by a delicate network (PL 101, 

 fig. 2). (Compare PL 102-104, 111, 123, and also Taf. x. of Hertwig, loc. clt.). 



The calymma, or the extracapsular jelly-veil, is in the PniEODARiA always well 

 developed and usually much larger than the enclosed central capsule. The entire 

 volume of the calymma may be three to six times as great as that of the capsule in 

 the majority of this legion ; but in the large Aulacanthida, Aulosphserida, Coelo- 

 dendiida, Ccelographida, &c., the volume of the former is twenty to fifty times as great 

 as that of the latter, or even more. The jelly substance is rather firm and consistent, 

 clear, structureless, and becomes more or less intensely stained by carmine. In the 



