CHAPTER XVI 



ORDER 3 FORAMINIFERA d'ORBIGNY 



THE FORAMINIFERA are Comparatively large Protozoa, living 

 almost exclusively in the sea. They were very abundant in 

 geologic times and the fossil forms are important in applied 

 geology (p. 12). The majority live on the ocean bottom, moving 

 about sluggishly over the mud and ooze by means of their pseu- 

 dopodia. Some are attached to various objects on the ocean 

 floor, while others are pelagic in their habitat. 



The cytoplasm of the Foraminifera is ordinarily not dif- 

 ferentiated into ectoplasm and endoplasm. Contractile vacuoles 

 are usually absent. The cytoplasm streams out through the 

 apertures, and in perforated forms through the numerous pores, 

 of the test, forming rhizopodia which are fine and often very 

 long and which anastomose with one another to present a 

 characteristic appearance. The streaming movements of the 

 cytoplasm in the pseudopodia are quite striking; the granules 

 move toward the end of a pseudopodium and stream back along 

 its periphery. The body cytoplasm, is often loaded with brown 

 granules which are apparently waste matter. In some forms 

 such as Peneroplis pertusus (Fig. 76), these masses are extruded 

 from the body from time to time, especially prior to the forma- 

 tion of a new chamber. 



The test of the Foraminifera varies greatly in form and struc- 

 ture. When fresh, it may show various colorations — orange, 

 pink, red or brown. The majority measure less than one milli- 

 meter, although larger forms may reach frequently five milli- 

 meters. The test may be siHcious or calcareous. In some forms, 

 various foreign materials, such as sand-grains, sponge spicules, 

 etc., which are more or less abundantly found where these or- 

 ganisms live, are loosely or compactly cemented together by 

 pseudochitinous or gelatinous substances. Certain forms show a 

 specific tendency in the selection of foreign materials for the 

 test. Silicious tests are comparatively rare, being found in 



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