Chapter 20 

 Order 5 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. 9). The majority live on 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. 



The cytoplasm is ordinarily not differentiated into the two 

 zones and streams out through the apertures, and in perforated 

 forms through the numerous pores, of the shell, forming rhizo- 

 podia which are fine and often very long and which anastomose 

 with one another to present a characteristic appearance (Fig. 5). 

 The streaming movement of the cytoplasm in the pseudopodia 

 are quite striking; the granules move toward the end of a pseu- 

 dopodium and stream back along its periphery. The body cyto- 

 plasm is often loaded with brown granules which are apparently 

 waste matter and in some forms such as Peneroplis pertusus 

 (Fig. 160), these masses are extruded from the body from time 

 to time, especially prior to the formation of a new chamber. Con- 

 tractile vacuoles are usually not found in the Foraminifera. 



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

 ture. When alive, it may show various colorations — orange, red, 

 or brown. The majority measure less than one milhmeter, al- 

 though larger forms may frequently reach several millimeters. 

 The test may be siliceous or calcareous and in some forms, vari- 

 ous foreign materials, such as sand-grains, sponge-spicules, etc. 

 which are more or less abundantly found where these organisms 

 live, are loosely or compactly cemented together by pseudochiti- 

 nous or gelatinous substances. Certain forms show a specific 

 tendency in the selection of foreign materials for the test (p. 38-39). 

 Siliceous tests are comparatively rare, being found in some spe- 

 cies of Miholidae inhabiting either the brackish water or deep sea. 

 Calcareous tests are sometimes imperforated, but even in such 

 cases those of the young are always perforated. By far the ma- 

 jority of the Foraminifera possess perforated calcareous tests. The 



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