132 



THE FORAMIN1FERA 



the chamberlets with one another is similar to that described in 

 Heterostegina. The variations on this arrangement which occur 

 result from a more speedy attainment, in different degrees, of the 

 cyclical growth. Where the nuclear characters have been recog- 

 nised, a single large nucleus was found in one of the large central 

 chambers of the megalospheric form. 



FIG. 58. 



Photograph of the central part of the section of Cyclodypeus carpenteri (microspheric) repre- 

 sented in Fig. 57, B. 



Looking back on the evidence furnished by these three genera 

 we find that Operculina is built on the same plan in both micro- 

 spheric and megalospheric forms ; that Heterostegina repeats the 

 operculine condition in both forms, though the number of un- 

 divided chambers is greater in the microspheric form than in the 

 megalospheric ; and that Cyclodypeus repeats both the operculine 

 and heterostegine conditions in the microspheric form, while in 

 the megalospheric the operculine stage is omitted or represented 



