Chapter 19 

 Order 4 Testacea Schultze 



THE Testacea or Thecamoeba comprise those amoeboid or- 

 ganisms which are enveloped by a simple shell or test, within 

 which the body can completely be withdrawn. The shell has usu- 

 ally a single aperture through which pseudopodia protrude, and 

 varies in shape and structure, although a chitinous or pseudo- 

 chitinous membrane forms the basis of all. It may be thickened, 

 as in Arcella and others, or composed of foreign bodies cemented 

 together as in Diflflugia, while in Euglypha siliceous platelets or 

 scales are formed in the endoplasm and deposited on the mem- 

 brane. 



The cytoplasm is ordinarily differentiated into the ectoplasm 

 and endoplasm. The ectoplasm is conspicuously observable at the 

 aperture of the shell where filopodia or slender ectoplasmic lobo- 

 podia are produced. The endoplasm is granulated or vacuolated 

 and contains food vacuoles, contractile vacuoles and nuclei. In 

 some forms there are present regularly in the cytoplasm numerous 

 basophilic granules which are known as 'chromidia' (p. 35). 



Asexual reproduction is either by longitudinal fission in the 

 forms with soft tests, or by transverse division or budding, while 

 in others multiple division occurs. Encystment is common. Sexual 

 reproduction by amoeboid or flagellate gametes has been re- 

 ported in some species. 



The testaceans are mostly inhabitants of fresh water, but some 

 live in salt water and others are semi-terrestrial, being found in 

 moss or moist soil, especially peaty soil. 



Shell simple and membranous 



Filopodia, often anastomosing Family 1 Gromiidae 



Pseudopodia filose, simply branched. . .Family 2 Arcellidae (p. 327) 

 Shell with foreign bodies, platelets, or scales 



With foreign bodies Family 3 Difflugiidae (p. 334). 



With platelets or scales Family 4 Euglyphidae (p. 339). 



Family 1 Gromiidae Eimer et Fickert 



These forms are frequently included in the Foraminifera by 

 other authors. 



Genus Gromia Dujardin (Allogromia, Rhynchogromia, Diplo- 



323 



