REPORT ON THE RADIOLARIA. XXxi 



these tracts, on the outer aspect of which run the longitudinal myophane fibrillje of the 

 podoconus (compare §§79 and 99). 



The porous area of the Monopylea was first described by Hertwig in 1879, and shown to be 

 the characteristic main-opening of the central capsule in various families belonging to this legion 

 (L. N. 33, pp. 71, 73, 83, 106, Taf. vii., viii.). According to his view "the capsule-membrane in 

 the porous area becomes thickened arouud each pore into a rod, perforated by a canal," and the 

 intracapsular protoplasm passes outwards through these fine canals (loc. cit., p. 106). I am not 

 able to share this interpretation, but think rather that I have convinced myself by the examination 

 of some living Nassellaeia, and of many well-stained and preserved preparations in the Challenger 

 collection, that the rods are solid, specially modified portions of the capsular wall, and that the 

 protoplasm does not pass through them but through pores which lie between them. 



60. J7ie Capsule-Openings of the Cannopylea {or PhcBodaria). — The capsule- 

 membrane of the Cannopylea always possesses only a single large main-opening or 

 osculum, which lies at the basal pole of the vertical main axis, and is closed by a circular 

 radiated hd (operculum radiatum). This operculum aj^pears, when seen from the surface, 

 as a sharply defined stellate area (astropyle), from the middle of which arises a shorter or 

 longer cylindrical tube, the proboscis. Hence the PhyEODARIA, like the Monopylea, 

 belong to the " Merotrypasta " or "Osculosa"; the structure and significance of the 

 circular operculum, which closes the main-opening (osculum), are, however, quite diflferent 

 in the two legions. Whilst the operculum of the Monopylea (porochora) is perforated 

 by numerous fine vertical pores, and connected with the peculiar internal pseudopodial 

 cone (podoconus), this structure is entirely wanting in the Cannopylea, and instead of it 

 there is a solid opercidum, with radial ribs which originate at the base of its central 

 tubular mouth ; this tube (proboscis) is cylindrical, often conical at the base, of very 

 variable length and with a round aperture at either end. In spite of the great difference 

 which the various families of Cannopylea exhibit in the formation of their skeleton and 

 its appendages, the constitution of this characteristic stellate main-opening (astropyle) is 

 always essentially the same ; both the stellate operculum itself, and the proboscis which 

 rises from its centre, show only slight differences in the various groups. In addition to 

 this large main-opening most Ph.eodaria possess several small accessory openings 

 (parapylae) ; and usually two of these are present, placed symmetrically right and left of 

 the aboral pole of the main axis and in the frontal plane (PI. 101, figs. 2, 6, 10 ; 

 PI. 104, figs. 1, 2a). Sometimes there are more numerous accessory openings (three to 

 six or more) regularly arranged, as in the two peculiar famUies, Circoporida and 

 Tuscarorida ; occasionally also there is only a single parapyle, at the aboral pole of the 

 main axis {e.g., in Tuscaridium) . The parapylae seem to be quite absent in the families 

 Challengerida, Medusettida, Castanellida, and perhaps also in other Ph^odaria. The 

 form and structure of the small accessory openings appear to be always the same. The 



