ON THE LIFE-HISTORY OF THE FORAMINIFEBA. 155 



As in Brady's specimens, the young shells are set in the brood 

 chambers, with their plane at right angles to that of the portion 

 of the disc which contains them. Fig. 43 represents a vertical 

 radial section through a disc containing young, and fig. 44 a 

 vertical tangential section of such a disc. It will be seen that 

 a considerable amount of protoplasm is present in the brood 

 chambers, filling in the interstices between the young shells. 

 This generally contains great numbers of the small alg^, but I 

 have failed to find any nuclei in it. It is, no doubt, continuous 

 through the pores of the shells with the protoplasm of the 

 young. 



When the central region of the disc is thus left empty, the 

 large parasitic algse contained in it, which are too large to pass 

 through the channels connecting the chamberlets with one 

 another, are found in active division, their reproductive phase 

 following that of their host. 



This species is often found attached to the green ovate 

 leaves of a plant which grows in the shallow water on the reef 

 On one occasion when I had brought in some large specimens 

 and put them with the leaves in a dish of water, in the course 

 of a few hours I found numbers of the megalospheric young 

 which had escaped from a shell and lay scattei'ed over the 

 leaves and the surface of the parent, whose large brood chambers 

 were empty. 



The large shells lie flat on the leaves, but the young ones 

 with few rings of chamberlets or none, often cruise about on 

 the edge of the disc, which is thus directed vertically to the 

 supporting object. Sometimes, when the specimens were kept 

 in dishes, the young shells were found floating at the surface 

 of the water with a film of pseudopodia extended about them, 

 in the same manner as pond snails often float supported by a 

 raft of mucus. 



The Megalospheric Form. — As stated above, the megalo- 

 spheric form begins its existence with a single nucleus situated 

 in the primordial chamber (figs. 46-48). This nucleus main- 

 tains its position during a greater part of the period of growth. 

 Thus among thirty-one examples of the megalospheric form in 



