ON THE LIFE-HISTORY OF THE FORAMINIFERA. 165 



In several species the second chamber of the megalospheric 

 form is peculiar. Thus, in Orbitolites, it forms the large cir- 

 cumambient chamber (Carpenter) which almost surrounds the 

 primordial chamber (megalosphere) ; in Oycloclypeus the second 

 chamber has a similar relation to the megalosphere. In Poly- 

 stomella it is not so large in proportion as in these forms, but 

 it is applied to the megalosphere for the whole of its length. 

 In other species the second chamber differs little in shape from 

 those which follow it. 



The size attained by the complete shell is, in some species, 

 markedly different in the two forms, while in other species this 

 difference does not exist. 



In Nummulites the microspheric form grows to a much 

 larger size than the megalospheric. In Polystomella, however, 

 the two forms attain about the same size. 



Among the Miliolidse, according to Schlumberger, the 

 microspheric form is usually the larger, but in Adelosina poly- 

 gonia, Schlumberger, the megalospheric form attains a rather 

 larger size than the microspheric (1"5 to 1'4 millim.). 



(c) The character of the nuclei. 



In Polystomella crispa (LiNN.) it has been shown that in 

 the megalospheric form a single large nucleus is present during 

 the greater part of the life of the individual, while in the micro- 

 spheric form numbers of smaller nuclei are found. How 

 far this contrast in the nuclei in the two forms is of general 

 occurrence among the Foraminifera remains to be seen. In 

 Rotalia Beccarii (Linn.), and Calcarina hispida (Brady), in 

 which I have seen the nuclei of both forms, the condition was 

 similar to that found in Polystomella, the megalospheric forni 

 having a single large nucleus, the microspheric form several 

 small ones. 



In Oycloclypeus, in which I have only seen two megalospheric 

 forms, a single large nucleus was present. 



In Orbitolites the conditions of the nuclei found in the two 

 forms are, on the whole, similar, but a phase is here presented, 

 the production of megalospheric young by megalospheric parents, 

 of which I have no evidence in Polystomella. 



