SKELETAL OR SUPPORTING STRUCTURES 



41 



of the body which enables the organism to attach itself temporarily. 

 In the case of Giardia {Lamblia) the ventral surface develops a large 

 sucking disc, by means of which the flagellate is able to attach itself to 

 the surface of the intestinal cells (Fig. 291). Amongst the Ciliata Stentor, 

 which is conical in shape, is able to fix itself to objects by pseudopodium- 

 like processes at its tapering posterior end (Fig. 22). 



SKELETAL OR SUPPORTING STRUCTURES.— It has already been 

 pointed out that some Protozoa are able to build for themselves pro- 

 tective external coverings. Amongst 

 the Rhizopoda these are seen typically 

 amongst the Foraminifera and Radio- 

 laria. The shells may be strengthened 

 by the adhesion of granules of sand, 

 spicules, or other material. In the 

 Foraminifera the shells are external 

 coverings, the pseudopodia being pro- 



FlG. 23. — CiLIATES WITH LORIC.E AND 



Opercula which Close the Orifice 

 WHEN Retraction Occurs ( x 250). 

 (From Lankester, 1903, after Kent 

 AND Wright.) 

 1. CotJiurinaaffinis. 2. Cothurinavalvala. 



Fig. 24. 

 (From 



teres ( x 660). 

 1912, after 



Schewiakoff, 1896.) 



N, Macronucleus ; n, micronucleus ; o, 

 mouth; ces., oesophagus with rod-like 

 supports; f.v., food vacuoles; c.v., con- 

 tractile vacuole; al, alveolar layer; st, 

 meridional rows of cilia; «., anal opening. 



truded through an opening as a snail emerges from its shell (Fig. 8). 

 In the Radiolaria the skeletal supports are more complicated, and 

 consist of spherical or asymmetrically formed fenestrated shells, 

 strengthened by various radially or tangentially arranged spicules 

 embedded in the cytoplasm (Fig. 78). The cup-like loricae found 

 amongst the Mastigophora (Fig. 18, i) and Ciliata (Fig. 23) may be 



