1894.] the Life-History of the Foraminifera. 157 



6 1 /* in diameter and provided with two flagella, one longer thanthe- 

 other, rising close together from the body of the spore. I am. unable to 

 say whether the parent of these spores was megalospheric or micro- 

 spheric, but as the isospores are produced by the individuals of the 

 former type it is possible that the anisospores belong to those of the 

 latter. 



Orbitolites complanata, LamJc. 



In the Microspheric form, the centre of the disc is occupied 

 by small chambers. Numbers of rounded nuclei are distributed 

 through the protoplasm, often in pairs, and in some cases they may 

 be seen to be united by a constricted band, as though in process of 

 simple division. Larger solitary nuclei with a well marked reticulum 

 are also present. 



In the later stages of growth large brood chambers are formed at 

 the periphery of the disc, which Brady found to be crowded with 

 young (" primitive discs ") of the megalospheric form. Examination 

 of specimens preserved in spirit in which the young are present in the 

 brood chambers, shows that the inner part of the shell is empty, its 

 contents being represented only by the young. A large nucleus is 

 present in the " primordial chambers " of the young discs. 



The centre of the Megalospheric form is occupied by the " primitive 

 disc." This consists of a large " primordial chamber " (the megalo- 

 sphere), which is usually pyriform, and measures about 100/t in 

 length, surrounded by the very large " circumambient chamber." 

 The small chambers of the remainder of the disc are arranged about 

 the primitive disc in rings. 



The nucleus which, as has been said, occupies the primordial 

 chamber in the young form, maintains that position during a large 

 part of the growth of the shell. Ultimately it appears to break up 

 into irregular fragments, which become dispersed through the adjoin- 

 ing chambers. 



The specimens of this form from Celebes have all attained a larger 

 size than those from Tonga and Fiji. In three cases (out of 114) the 

 protoplasm has left the central region of the disc, and is massed in 

 brood chambers at the periphery in the form of megalospheric young, 

 exactly resembling in shape and size those borne by the microspheric- 

 form. It is thus established that both the megalospheric and micro- 

 spheric forms of Orbitolites under certain circumstances, produce 

 young of the megalospheric type. 



An examination of specimens of Botalia beccarii (Linn.), Truncat- 

 ulina lobatula, Walker and Jacob, Calcarina hispida, Brady, and Cyclo- 

 clypeus has furnished evidence of the relation of nuclear characters 

 to the two forms of a species analogous to that obtained in 

 Polystomella. 



