8 SITALL(^W-\VATKn FORAMINIIERA OF TORITJGAS REGION. 



In Orbitolites duplex the pseudopodia were very straight and 

 slender, extending out rapidly to a distance ecjual to the diameter 

 of the test. They are put out in groups of 3 to 12 from each of the 

 marginal apertures of the test. There is very little coalescing in 

 the psoutlopodia of Orbitolites duplex in contrast with Iridin diaphana, 

 where anastomosing is of usual occurrence. In Orbitolilcs, pseudo- 

 podia an inch in length were several times noticed. One specimen 

 of Orbitolites was broken in being taken from a leaf of Posldonia and 

 the two halves of the test were separated, leaving a clear space 

 entirely across, after which pseudopodia were sent out from the 

 entire periphery. In Haliphysema advena the pseudopodia were very 

 slender and showed little tendency to join. 



One important observation was that in the case of Iridia diaphana 

 taken from Posidonia leaves and placed in Petri dishes over night. 

 In the morning some of these were found to have left their test 

 empty and were moving about as naked masses of protoplasm with 

 a free and comparatively rapid movement. That the animal may 

 leave the test and pass some time without one is very significant 

 from the standpoint of the method of growth. Growth of the test 

 in those species which have a single chamber has often been a subject 

 of speculation. If the test can be abandoned at will and another 

 secreted or made by collecting more material in the case of those 

 which have agglutinated tests, this difficulty is solved, and we may 

 also understand how various sedentary species can collect various 

 materials which are not common for their tests. Given free move- 

 ment and a power of discrimination, which seems to be a character- 

 istic of certain species, it is not difficult to explain how such tests 

 are made of one sort of building-material — spicules, mica flakes, 

 ambulacral plates of brittle-stars, etc. The occurrence of specimens 

 of Iridia on Posidonia some inches above the bottom, while its 

 test is made of material from the bottom is also explained. The 

 material could easily be carried up to this elevation while ingested 

 in the moving mass of protoplasm, and then sent out to the sur- 

 face when the animal settled down to build the test. 



Table 1. 



The movement of the whole animal without the test was observed 

 and measured in Iridia diaphana, and with the test in Discorbis 



