318 Mr, H. J. Carter on the Structure of the Foraminifera. 



at the moment of being broken up in water, and a third sub- 

 jected to a very weak solution of nitric acid and water for a night, 

 with the following results : — 



It was found that, in the latter experiment, the chambers and 

 the canals, after having been gradually deprived of their calca- 

 reous matter, still retained their form in a membranous state 

 (PI. XVII. fig. 12) ; and under this condition they will now be 

 described. 



Chamber. — The horizontal or exposed walls of the chamber, 

 in a membranous state, present a number of semi-opake circular 

 bodies arranged in a pavement-like form close together, each of 

 which has a depression or hole in the centre, and these corre- 

 spond to the "vertical tubuli ;; (fig. 12 a, b) ; while the septal 

 borders (c) are composed of a transparent membrane without 

 these bodies, but pierced here and there with large holes (//), 

 from which tubes are extended to the interseptal canals. The 

 marginal border of the chamber is also supplied by a transparent 

 membrane loosely attached to the spicular cord, but the base or 

 internal margin is firmly fixed to the marginal plexus of canals, 

 now, of course, in the way we are examining them, all rendered 

 membranous by the absence of the calcareous matter. 



The chamber thus reduced to a membranous state is found to 

 contain in its cavity various bodies (fig. lie), viz. small and 

 large spherules (figs. 13, 14), and starch-grains, to which we 

 will now severally direct our attention. 



Small spherule (fig. 13). — This consists of a spherical portion 

 of semi-opake homogeneous matter, surrounded by a delicate 

 spherical transparent cell, l-5400th of an inch in diameter. 

 The chamber may contain a few only, or be crammed with 

 these bodies ; and they are observed to be attached in masses to 

 branched stems or filaments, like bunches of grapes. 



Large spherule (fig. 14). — The large spherule consists of a 

 spherical portion of homogeneous matter charged with granules 

 and enclosed in a spherical transparent capsule about l-1800th 

 of an inch in diameter. The capsule is not always visible, if 

 present, and the form frequently slightly elliptical, while the 

 colour is sometimes yellowish by transmitted light, like that of 

 dried albumen, and at others white by reflected light, as if there 

 were calcareous matter in it ; perhaps the former difference may 

 be from drying or pressure, while the latter is evidently that of 

 advancement in development. 



Starch-grains. — These are thin, flat, and variable in size, but 

 otherwise bear the unmistakeable characters of the " starch- 

 grain." They were not numerous, but always present, and, 

 with many portions of the other soft substance of the cavity 

 of the chamber, became purple and blue respectively, under the 



