348 BIOLOGY OF THE PROTOZOA 



Order IV. TRIPYLEA, Hertwig. 



In this great group of the Radiolaria all forms agree in having a 

 central capsule with three openings. .One of these, the astropyle, 

 is the main or primary opening, the others, parapyles, are secondary. 

 The primary opening is at the base of the main axis of the capsule 

 and is covered by a radially-striped membrane the center of which 

 is drawn out into a tube the opening of which is surrounfled by a 

 mass of secretory material and ])igment the pheodium. Hence 

 Haeckel's name for the order the Pheodaria. 



The bars of the silicious skeletons are hollow in the main, although 

 solid parts may also occur. 



Haecker divides the Tripylea into six groups of families which 

 Doflein ranks as Legions but we designate them here as Sub-orders. 



Sub-order 1, Phseocystina, Haeckel. 



These are either naked forms or provided with a simple skeleton 

 of numerous hollow bars which arise either independently in the 

 protoplasm or are bound together to make a star-form groiqj. 



FamUy 1. Aulacanthidae, Haeckel.— Here the skeleton consists 

 of hollow radial spines and a mantle of very fine tangential tubes. 

 (Aulacantha scolymcmtJia, Haeckel.) 



Famih/ 2. Astracanthidae, Haecker. —Forms with radially arranged 

 hollow spines, the distal ends of which are variously developed while 

 the proximal ends come from the outer surface of a central, hollow 

 sphere. The central capsule here, is double. 



Sub-order 2. Phaeosphseria, Haeckel. 



The skeletons of these forms consist of one, or two concentric 

 shells; shell-openings if present, are limited to the inner shell. 



Family .3. Aulosphseridae, Haeckel. —Skeletons in the form of a 

 simple latticed shell formed by hollow radial bars and a tangential 

 raeshwork; no shell opening present. 



Family 4. Cannosphseiidse, Haeckel.— Here the skeletons are com- 

 posed of two concentric shells bounrl together by radial bars; the 

 inner shell has an opening (pylom). 



Farnily 5. Sagosphseridse, Haeckel. — With one or two concentric 

 shells without shell openings; the bars of the mesh work are solid, 

 thin and flexible. 



Sub-order 3. Phaeocalpia, Haeckel. 



Shells monaxonic or polyedral with })yl(im or opening and with 

 radial spines variously arranged. 



