KO. 4 FORAMINIFERA CUSHMAN 



STRUCTURE OF THE TEST 



In the fresh water foraminifera, which are all of a distinct family 

 from the marine ones, a calcareous or agglutinated test is not devel- 

 oped. What test is formed, is of a gelatinous or flexible chitinous 

 material. In what may be called the more typical forms, the test is 

 either formed by the cementing together of foreign particles or by 

 the secretion of a calcareous test. In the first group, the animal gets 

 its material from the ocean bottom itself. This may consist of the 

 ocean mud, sand, sponge spicules, mica flakes, etc. In some species, a 

 definite selection seems to take place, and one kind of material is 

 used to the exclusion of others. The most striking examples of this 

 are species of Psatnmosphaera. P. fuse a Schulze uses only sand grains 

 of various sizes, cementing them into a spherical test. P. parva Flint 

 uses sand grains of very uniform size and adds to its test a large 

 acerose sponge spicule projecting at either side. P. testacea (Flint) 

 uses the tests of other foraminifera and ignores sand grains which 

 are present in the bottom material. P. hozvmanni Heron- Allen and 

 Earland makes a test entirely of mica flakes, and P. rustica Heron- 

 Allen and Earland of sponge spicules. 



Some species of foraminifera which secrete a calcareous test also 

 cover the outside with sand or other fragmental material. These are 

 not true agglutinated tests however, any more than in the case of 

 certain molluscs which cover their shells with fragmental material. 



Of the calcareous secreted tests there are two main groups, the 

 perforate and imperforate. In the former the test has great numbers 

 of small pores, while in the latter (MiHolidae) the test is normally 

 without pores and has a peculiar white appearance, whence the name 

 " porcellanous " often applied to the foraminifera belonging to this 

 family. Under brackish conditions and in deep water where calcareous 

 tests are easily dissolved, very thin tests are found of chitinous or 

 even siliceous material. 



The test may be simple as in many of the Lagenidae or Rotaliidae, 

 or become complex with internal radiating canals as in the Num- 

 mulitidae. In some genera very interesting structures are developed, 

 as in the " balloon " and " float " chambers in Trctompliahis. 



DEVELOPMENTAL STAGES 



As already noted from the habits and life history of the foramini- 

 fera, adult tests are the rule in any collection. There are, however, 

 always some specimens which have not yet reached their adult stage 

 and which show development. These stages show definite conformity 



