ROTALIIDAE — TRETOMPHALUS. 43 



the bottom specimens may thus be accounted for can not be stated 

 with any degree of certainty. It seems possible that the enlarged 

 "balloon-chamber" is developed from a bottom-living form, as many 

 species adapted to a pelagic life develop a more or less inflated 

 final chamber with large pores. These evidently allow free passage 

 of the protoplasm, which, being extended and containing gases, 

 floats the test without difiiculty. Sir John Murray, while on the 

 Challenger, observed living specimens of Tretomphalus bulloides, filled 

 with ''flagelli spores (?)" which were then noted and have since 

 been referred to by various authors. These had small bodies at 

 one side which took stain more freely than the general mass. 



In the tow-nets in the work at the Tortugas I frequently took 

 Tretomphalus bulloides at the surface, especially in the open waters 

 off Loggerhead Key. Some of these had the "float-chamber" con- 

 taining a large air (?) bubble about half the diameter of the test. 

 Murray also noted this in his fresh material. In these pelagic 

 specimens there were often swarms of what were apparently zoo- 

 spores, capable of rapid movement, but showing no flagellse or ciUa, 

 so far as could be observed. It was suggested by Earland that 

 these might be discharged and on rupture of the "balloon-chamber" 

 the upper rotaUform portion might settle down to the bottom again 

 and live on as Discorhis or as Cymbalopora poeyi. My own observa- 

 tions would tend to disprove this, for in all the specimens observed 

 no protoplasmic mass was left in the rotaliform portion, this also 

 being filled with zoospores, as was shown by crushing this part 

 when none were observed in the "float-chamber." On crushing 

 such specimens, numbers of zoospores came from the smaller cham- 



FiG8. 2, 3. — Tretomphalus bttUoidee 

 (d'Orbigny). 



2. Dorsal side, showing change in size 



of pores in progressive chambers. 



3. Outline of ventral side after removal 



of final chamber. 



bers of the rotahform portion, but no undifferentiated protoplasm. 

 Murray has already noted that none of his pelagic specimens con- 

 tained the ordinary form of protoplasm seen in the other For- 

 aminifera. These zoospores are so minute (0.001 to 0.0015 mm.) 

 that they could easily pass through the pores of the spherical 

 "balloon-chamber" and to it from any part of the rotaliform 

 portion through the apertures of the early chambers. 



In connection with this, another very interesting fact was noted 

 in regard to the coloration of the initial portion of the test. It 



