COMPARATIVE ANATOMY 



CHAP. 



Sub-Class III. Heliozoa. 



Globular Sareodina, naked or clothed with a siliceous skeleton, with fine more 

 or less stiff pseudopodia radiating on all sides. Contractile vacuoles generally 



IJresent in varying numbers. Actinophrys 

 (Fig. i), ActiHosphceriiim, Acanthoeystis, Clath- 

 rulina. 



Sub-Class IV. Eadiolaria. 



Body divided by an originally spherical or 

 egg-shaped capsular membrane into an outer, 

 and an inner, nucleated portion (outer and 

 inner capisules). The outer capsule consists of 

 protoplasm (without nucleus) and of a gela- 

 tinous envelope (calymna). The protoplasm 

 forms a layer roimd the inner capside and a 

 network round the calymna, these two being 

 connected by means of protoplasmic threads. 

 Fine flexible pseudopodia radiate in all directions 

 from the surface of the calymna. Skeletons 

 of extraordinarily various shapes, of silica or of 

 chitin-like organic substance (aeanthin), are seldom wanting. The extra- and intra- 

 capsular protoplasm are connected through various openings in the cell-membrane. 

 This division of the marine Sareodina is wonderfully rich 

 in forms and shapes. Without contractile vacuoles. Uni- 

 cellular algjE (yellow cells) live symbiotically with the 

 Radiolaria. The family of the Polycyttaria among the 

 Spumellaria is distinguished by the formation of colonies. 



A. Porulosa. 



Central capsule spherical, without a principal aperture, 

 with innumerable fine pores. 



I. Spumellaria. — Nucleus central, dividing late in the 

 life of the iudividual. Skeleton siliceous or wanting, never 

 penetrating into the intra-capsular protoplasm. Tlialassi- 

 colla, Collozoum, Sphmrozoum, Thcdassoplancta (Fig. 5), 

 OoUosphxra, Dictyastrum. 



II. Acantharia. — Nucleus eccentric, dividing early. 



Fio. 4.— Aotinophrys sol, after Gre- 

 nadier, p, Pseudopodia ; n, nucleus ; a, 

 axial filaments of the pseudopodia. 



Fig. 5.— Thalassoplanota 

 lirevlspicula, part of a sec- 

 tion, after Haeckel. Icm, 

 Capsular membrane ; ip, 

 intra-capsular ; ep, extra- 

 capsular protoplasm ; ti, 

 nucleus ; ill, nucleoli ; ot, 

 oil-drops ; m, alveolar ca- 

 lymna;rp, protoplasm on Skeleton of aeanthin, radiating from the centre of the 



Fio. C— Phractaspis prototypus (after Haeckel), skeleton. 



the surface of the calymna ; 

 , spicules. 



central capsule. Acanthovietra, Phractaspis (Fig. 6). 



