ON THE LIFE-HISTORY OF THE FORAMINIFERA. 153 



radial section at right angles to the plane of the disc is Y- 

 shaped (fig. 43). 



The shells whose margins present this character, and which 

 have only been obtained from Fiji and Tonga, have been 

 separated as a distinct variety, named "laciniata" (Brady). 

 So far as I have seen they are all microspheric. 



I may further recall the fact that the peripheral annuli of 

 the full grown disc of this form are often found to be not 

 divided up into small cubical or columnar chambers, as are 

 those lying nearer the centre, but are composed of spacious 

 chambers extending vertically through the whole thickness 

 of the disc, and circumferentially round a considerable portion 

 of its circuit. These may be called the brood chambers (fig. 43). 

 In specimens which Brady obtained from the reefs of Fiji these 

 chambers contained multitudes of young shells, consisting of the 

 "primitive discs" of the megalospheric form. 



I have now to give the results of my examination of 

 preserved specimens. 



Microspheric Form. — All the examples of this form which 

 I have examined, were full grown or nearly so. As above stated, 

 the central part of the shell is occupied by small chambers. I 

 have not been able to distinguish the central chamber (micro- 

 sphere) from those which surround it, in the preparations I have 

 seen. 



Before the young are formed, the protoplasm fills all 

 the chambers of the disc, with the exception of the brood 

 chambers, which contain only a thin lining of protoplasm. This 

 may in part be due to the withdrawal of the protoplasm as the 

 result of the action of the spirit. 



In the specimens of which I have cut sections (fourteen), 

 numbers of small rounded nuclei are thickly scattered through 

 the protoplasm, so that two or more often appear in the section 

 of a single chamber (fig. 41). The great majority of these are 

 about 6 to 10 /i in diameter, but some reach 20 fi. 



A reticular structure may often be seen in the nuclei, and 

 small darkly-stained masses, which appear to be nucleoli, are 

 seen near the peripheral parts of the nucleus. The smaller 



