CHAPTER XIV 



CLASS 2 SARCODINA BUTSCHLI 



THE MEMBERS of this class do not possess any definite pellicle 

 and, therefore, are capable of changing the body form and 

 forming pseudopodia. The term "amoeboid" is often used to 

 describe their appearance. The pseudopodia serve for both loco- 

 motion and food-capturing. The peripheral portion of the body 

 shows no structural differentiation in Amoebaea, Proteomyxa, 

 and Mycetozoa. Internal or external skeletal sturctures are 

 variously developed in other orders. Thus in Testacea and 

 Foraminifera, there is a well-developed test, or shell that usu- 

 ally has an aperture, through w^hich the pseudopodia are ex- 

 truded. In Heliozoa and Radiolaria, endoskeletons of various 

 forms and materials are developed. 



Unlike the Mastigophora or the Ciliata, the Sarcodina lack 

 permanent cell-organs for capturing and ingesting the food mat- 

 ter, although some of them possess semi-permanent axopodia. 

 The cytoplasm, as a rule, is differentiated into the ectoplasm 

 and the endoplasm, but this differentiation is not constant. 

 In Radiolaria, there is a perforated membranous "central cap- 

 sule" between the ectoplasm and endoplasm. The endoplasm 

 contains the nuclei, food vacuoles, various granules, and con- 

 tractile vacuoles. The majority of the Sarcodina are uni- 

 nucleate, but numerous species of Foraminifera and Mycetozoa 

 are multinucleate. In one group (Paramoebidae), there is a 

 peculiar "secondary nucleus." 



The Sarcodina are typically holozoic, but in a few cases holo- 

 phytic. The food consists of Protozoa, small Metazoa, and 

 Protophyta, which present themselves conspicuously in the 

 cytoplasm. One or more contractile vacuoles are invariably 

 present in forms inhabiting fresh water, but absent, as a rule, 

 in parasitic forms or in those which live in salt water The 

 Sarcodina vary in size from a few microns up to several milli- 



[176] 



