154 PROCEEDINGS OF TEE NATIONAL MUSEUM. vol.57. 



forth from the exterior. The only connection between the central 

 cavity of the test and the exterior seems to be tlii'ough these radial 

 channels. When placed with the convex side downward the chitinous 

 layer may be gently pressed, causing the protoplasmic mass of the 

 central portion to sway back and forth; but it is held firmly within 

 the chitinous envelope unless this is ruptured by the rough treatment. 

 The chitinous layer is, however, tough and capable of considerable 

 resistance. 



By reflected light the protoplasmic portion is of a peculiar light 

 yellowish brown color against the white of the sand grains of the 

 test with the lines of the radial channels and the peripheral portion 

 of the central mass of a deeper orange color. With high power this 

 deeper color is seen to be due to the presence of great numbers of 

 unicellular algae, which seem to be rather closely confined to these 

 areas or at least to be concentrated there in greater numbers. These 

 algae are brownish in color, of very uniform size, about 6-7 /x in length 

 and apparently have a commensal relation with the protozoan as 

 will be noted later. 



Usually within five minutes after the foraminifer has been de- 

 tached from the Posidonia and placed in fresh sea water pseudopodia 

 appear at the periphery. These are thrust out rapidly and carry with 

 them numbers of the unicellular algae already mentioned. These 

 seemingly adhere to the sides of the fine pseudopodia, as shown in 

 plate 19, figure 3. The pseudopodia themselves are largely of clear 

 protoplasm with fine "knots" at irregular intervals of slightly more 

 compact material. There is a tendency for the algae to collect at the 

 junctions of the pseudopodia. In the finer pseudopodia there is 

 often a movement in the opposite directions at the same tim-e, one side 

 carrying the ''knots" and algae outward, the other side carrying 

 them backward toward the test. This movement may be suddenly 

 interrupted and all flow in one way or the other or each become 

 reversed. When steadily moving the protoplasm of the finer pseudo- 

 podia is carried along at an average speed of about 1 mm. a minute 

 from actual measuments with micrometer scale and stop watch. 



The unicellular algae evidently have a comm.ensal relation to the 

 foraminifer, as they are usually associated with the pseudopodia. 

 When the pseudopodia are extended and active nearly all the algae 

 are outside the actual test and when quiescent they are apparently 

 stored in the area at the peripheral portion of the central mass and 

 in the radial channels, as already noted. 



The protoplasmic body of the animal has the power of leaving the 

 test at will. This was noted in cases where specimens were detached 

 and left over night in sea water and in the morning found at some 

 distancefrom their empty test. Whether this withdrawal was through 

 the radial canals or through some breaking down of the chitinous 



