90 Protozoa. 



centre of the animal, perforate the oontral capsule^ and the vanOuH 

 soft layers and project all over the surface. In others it foiiim a 

 latticed sphere perforated by many larg-e iipcM'tiiroH whilst spines 

 sometimes radiate from it to the surface (Fig. 49, B). in otJiei'K 

 again, there are several such H|)heres, enclosed one within the other 

 and connected by radial spines cvo.sHiug from one splievc^ to luiotliei' ; 

 if there are two such spheres one lies within, the other outsidii the 

 central capsule; if there are three, thc^ innermost may lie within Ihe 

 central nucleuis. in other cases the nliell is more discoid or dome- 

 shaped ; altogether the skeletons of this division offer the greiitost 

 variety of beautiful forms. 



Within the protoplasm of the central c!i]),sule there is a nucleus 

 (sometimes several) ; in that extc^rnii,! to the capsule there arci n(m- 

 contractile vacuoles; white, red, and yellow oil gh:)buleH; and red, 

 yfellow, and brown pigment. DtOiciitc^ pseudopodia usually 

 radiate on all sides from the thin layei' of protoplasm Hurrouiiding th(» 

 central capsule ; they often juui-stomosc^ 'rhoy jxirforate the traiis- 

 y)arent jelly veil and project into the watei' as long iilamoTits. in the 

 protoplasm external to thc^ capsule thei'c^ jire nunn^rouH vacuoles 

 which may also occur in the portions of the j)seiidopodia lying 

 in the jelly veil, so that the whole of the jelly lias a v(^si(uiliiT, 

 foamy appearance.* Food, consisting of unicellular plants !i,nd 

 animals, is caught by thc^ ])seudopodifi and drawn ird,o tlie 

 protoplasm. 



The reproductive processes ai-tMniper'i'c^ctly known, in some 

 forms the contents of the ccmtral capsule have been observed to 

 break up into a number of smaller cells each furnished with from 

 one to three long flagella, "swarin spores," whose idtimate fate is 

 unknown; it is only certain that thc^ capsule bursts and the sfiorcs 

 become free-swimming. t Some Radioiaria, in conso(juonce of repeii.t(!d 

 division, form colonies, the individuals of which iiro connect(!d by 

 a common jelly veil. 



Small yellow cells arc! frequently found in the Radiolaciii, ; 

 their existence used often to be citc'd as one of a number of points 

 indicating the multicellular structure of this group. Recnrnt rc^seiirchc^s 

 have, however, demonstrated that they arc! regally indepc^rnic^rd, 

 organisms, small Algee, which are piirasitic in the Rjidifjlariji,, or 

 more correctly, commerisal with them, for the org;in ism sr^ems rather io 

 profit than"to suffer by their presence, since like: otiier jilants they 



* The vacuoles, at least in some of the Kadiolaria, contain a watery fluid of a \em 

 flpeoific gravity than sea watur. The protoplaam contracts in regponBc to some 

 external Htimulus {e.g., the violent movements of the water), gome of the vacuoles an: 

 hurst and the animal sinks ; after a storm, tliorofore, there are no Radioiaria to tx^ 

 found at the surface. They rise again later on, in consequence of the reappearance of 

 the vacuoles. 



+ Sometimes in one and the same central cajwulo two kinds of spores arise, larger 

 and smaller, macro- svnd micro-spores. 



