258 A. EARLAND ON RADIOLARIA. 



The importance of tlie capsule membrane was first indicated by 

 Haeckel in his monograph '' Die Radiolarien,'^ published in 1862, 

 and his conclusions have been endorsed by Hertwig and other 

 workers. The capsule membrane appears to be almost invariably 

 present at one time or another of the Radiolarian life, and is 

 usually persistent for the greater part of its existence, but in 

 some species the membrane is only formed immediately before 

 sporification, and lasts but a short time. It possesses great 

 powder of resistance to chemical and physical reagents, com- 

 bining density with elasticity in a high degree. It is an 

 extremely thin and delicate membrane, usually structureless 

 except for its apertures, and hence may be easily overlooked ; 

 but its presence may always be detected by means of staining 

 fluids or other suitable reagents. 



In all Radiolaria the membrane is pierced with definite openings 

 through which the extra-capsular protoplasm communicates with 

 the sarcode in the interior of the capsule, and as these openings 

 or " pylae " (= gates) show characteristic or constant features, 

 they have been utilised by Haeckel as a basis for the classification 

 of the Radiolaria, which he divides into four legions : — 



(1) Peripylea or Spumellaria. 



(2) Actipylea or Acantharia. 



(3) Monopylea or Nassellaria. 



(4) Cannopylea or Phseodaria. 



In the first legion, the Peripylea or Spumellaria, the capsule 

 membrane is single and perforated by numerous extremely fine 

 pores equally distributed over the whole of its surface. 



In the second legion, the Actipylea or Acantharia, the capsule 

 membrane is single and also perforated by numerous extremely 

 fine pores; but they are fewer in number than in the first legion, 

 and are marked off into regularly arranged groups or lines by 

 imperforate intervals. 



In the third legion, the Monopylea or Nassellaria, the capsule 

 membrane is also single, but possesses only one large opening or 

 osculum. This is situated at the basal pole of the main axis, and 

 is closed by a circular perforated lid {oj^erculum porosum). Seen 

 from the surface, this lid appears as a clearly defined porous area 

 {porochora or area porosa) and forms the horizontal base of a 

 peculiar " pseudopodial " cone, which stands vertically in the 



