164 THE FLOATING ANIMALS 



the living matter (protoplasm), flowing out of the shell- 

 mouth and fine holes, to form a sort of bubbly lather 

 between them, and to put out long threads for the 

 capture of prey (Fig. 78). 



Another group of unicellular animals (the Radio- 

 laria), in which the living matter has much the same 

 character, either form no skeleton, or form it of some- 

 thing else than lime. Thus, Thalassicolla is a little ball 

 of clear jelly with a dark kernel ; and Collozoum is a 

 colony of similar animals, looking like little dots in a 

 common jelly ; these have no skeleton. But others 

 (Figs. 77, 79, 81) have beautiful skeletons of flint ; 

 in yet others (Fig. 80) the skeleton is formed of long 

 needles of a peculiar substance, radiating from a 

 common centre (Acanthometra) . Lastly, in an oceanic 

 group, of which at present little is known, the skeleton 

 is very varied in shape, and often of remarkable com- 

 plexity and beauty (Figs. 82 to 86). 



The two closely allied forms, Ceratium (Fig. 38, 

 p. 122) and Peridinium (Fig. 41, p. 123), enclosed in a 

 cuirass of plates, often occur in very large numbers ; 

 they are claimed by botanists as plants, but are also 

 classed by some zoologists as animals. Another form, 

 often very common off our own coasts, is Noctiluca 

 (Fig. 87), an important source of the luminosity or 

 so-called " phosphorescence," which lights up the water 

 at night when disturbed. 



Of marine unicellular animals which have no skeleton 

 little is known, for the reason that it is rarely possible 

 to study them alive on board, and practically impos- 

 sible to preserve them properly for examination on 

 shore ; consequently, careful drawings of such forms 

 alive and expanded are greatly needed ; to those 

 possessed of some zoological knowledge the naked 

 Ciliata and Flagellata may be commended. 



