THE FORAMINIFERA 



101 



pore at the margin of the disc, or into a chamber of the suc- 

 ceeding annulus, as the case may be. In this species the canals 

 all lie in one plane, which is the median plane of the disc (cp. 

 Fig. 38, i). 



n 



m 



FIG. 33. 



OrbitdUes niarginalis, Lauik. m, whole test ( x 20) ; A, centre of megalospheric, B, of micro- ' 

 spheric form, x 100 ; b, centre of latter, x 280 ; x, the outer end of the last series of cham- 

 berlets which follows the spiral mode of growth. The figures 3 and 11 in A and 6 mark the 

 last of the undivided chambers in the two forms respectively. 



The microspheric form (Fig. 33, B and b). The microsphere 

 opens directly, without the interposition of a spiral passage (as 

 appears always to be the case in the Peneroplididae), into the 

 first chamber. The chambers are arranged at first in a gradually 

 expanding spiral, eleven to sixteen simple chambers succeeding 

 one another as in the genus Peneroplis, but communicating by 



