OBSERVATION ON LIVING SPECIMENS OF IRIDIA 

 DIAPHANA, A SPECIES OF FORAMINIFERA. 



By Joseph Augustine Cushman, 

 Of the Boston Society of Natural History. 



While at the Tortugas laboratory of the Carnegie Institution of 

 Washington, tlu-ough the kindness of the director, Dr. Alfred G. 

 Mayor, I collected numerous foraminifera. Among these were 

 living specimens which are apparently identical with or close to the 

 species described by Heron-Allen and Earland as India diapliana K 



Specimens are attached to various objects but the most accessible 

 are those which are adherent to the broad leaves of Posidonia which 

 covers the bottom in shallow water in various places. 



In general the test of the Tortugas specimens of India is made 

 largely of calcareous sand grains (pi, 19, fig. 1) in a slightly raised 

 dome, but larger specimens usually are more or less irregular in out- 

 line. The upper surface only is composed of agglutinated material, 

 the lower surface and the lining of the upper side being of thin 

 chitinous material forming an enclosing membrane. The calcareous 

 material may be entirely dissolved in weak acid leaving this chitinous 

 envelope intact. In its living state viewed from above the interior 

 of the test is not visible, due to the opaque wall of sand grains. With 

 a thin scalpel the entire test may easily be removed from the leaf of 

 Posidonia and transferred to the water. If placed upside do'»\'n and 

 examined with low power more of the structure of the test can be seen. 

 A small sector of this is shown in plate 19, figure 2. Seen from 

 below there is at once distinguished a central more or less homogen- 

 eous mass of a light yellowish brown color surrounded by a slightly 

 darker periphery. Outside this is a peripheral band to the edge of 

 the test, of lighter color with practically no protoplasm in most of 

 the area, but here and there at intervals v/ith irregular bands passing 

 from the central protoplasmic mass to the periphery of the test. 

 These are of a light yellow color in general like that of the central 

 mass. In each of these radial bands appear several more or less dis- 

 tinct channels and from these the protoplasm streams back and 



1 Trans. Zool. Soc. London, vol. 20, 1914, p. 371, pi. 36. 



Proceedings U. S. National Museum, Vol. 57— No. 2308. 



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