242 The Sarcodina 



"chitinoid-siliceous" material which is usually, although not always, en- 

 crusted with sand grains. In Lecquereusia (Fig. 5. 29, A), sand grains or 

 diatom shells are ingested and then modified in form before addition to 

 the test (107). In the Euglyphidae (Fig. 5. 29, G-I), foreign particles are 

 replaced by scales, which are formed and stored in the cytoplasm prior 

 to fission. These scales are insoluble in hot sulfuric acid in Nebela collaris 

 and seem to be completely siliceous (87). The Euglyphidae are thought 

 to produce such scales from absorbed minerals, rather than by the modi- 

 fication of ingested particles. In Euglypha (47), it is possible to observe 

 cytoplasmic inclusions showing similar optical properties and forming a 

 graded series from small globules to typical scales. Such a "series" implies 

 a gradual growth of the scale by addition of material from the cytoplasm. 



The color of the test varies with the species and often to some extent 

 with the individual specimen. Various shades of yellow and brown are 

 the rule, and the color may become darker as the animal grows older. 

 The yellow-brown tests presumably contain iron, w^hile the occasionally 

 observed violet tints (Heleopera) are attributed to manganese. 



Pseudopodia. The pseudopodia of Testacida are of two general types, 

 slender lobopodia (Fig. 5. 29, B, C) and typical filopodia (Fig. 5. 29, G). 

 The former have rounded tips while the latter type tapers to a point. 

 Extended filopodia may show some degree of rigidity, although they are 

 flexible and may be swung about like sluggish flagella, as in Trinema 

 lineare (36). In addition to these clearly defined types, pseudopodia 

 somewhat intermediate in form have been described in Cryptodifflugia 

 and Cochliopodium. The form of the pseudopodia seems to be a reliable 

 taxonomic feature, and their relative number also may be fairly char- 

 acteristic. Such species as Hyalosphenia punctata (107) normally move 

 by means of one large pseudopodium. Other species typically extend 

 several pseudopodia at once. In addition to the usual functions, filopodia 

 in particular serve in attachment of Testacida to the substratum. 



Contents of the test. Within the cytoplasm are found the nucleus or 

 nuclei, ingested food, one or more contractile vacuoles, stored food, and 

 often reserve shell-plates (Euglyphidae) or ingested sand giains to be used 

 for construction of a new test. The majority of species have only one 

 nucleus, which usually lies near the aboral pole of the test. However, 

 Arcella (Fig. 5. 29, C) is binucleate, Avhile such large species as Diffiugia 

 urceolata (107) are multinucleate. The perinuclear cytoplasm ("chromid- 

 ium," "chromidial zone") of the Euglyphidae usually contains stored food 

 which, in Nebela collaris (87), consists mainly of a glycogen-like carbo- 

 hydrate. This chromidium has been implicated in various accounts of 

 the chromidial origin of nuclei. Since the chromidium is sometimes 

 stained so intensely that the nuclei are obscured, it was believed at one 

 time that the nuclei periodically disintegrate into chromidia to form the 

 chromidial zone. Since the nuclei could be seen in specimens without a 



