ON THE LIFE-HISTORY OF THE FORAMINIB'ERA. 151 



mately equal size. Their diameter in specimens killed in cor- 

 rosive sublimate and acetic acid is 4 /i. 



A simultaneous division of nuclei by karyokinesis imme- 

 diately before the formation of the reproductive elements, such 

 as occurs in the megalospheric form of Polystomella, is a 

 phenomenon of very general occurrence. 



Among the Mycetozoa it was shown by Strasburger (44) 

 to occur in Trichia fallax in the developing sporangium, and 

 later researches (21) have shown that it takes place immediately 

 before the formation of the spores in this and ten other species 

 belonging to eight genera. In three of these (Graterimn, 

 Didymium, Badhamia), as in Polystomella, the protoplasm 

 becomes aggregated about the dividing nuclei in rounded 

 masses before the ultimate division into spores. 



It appears probable that the phenomenon is akin to the 

 division of the micro-nucleus which precedes conjugation in the 

 Infmona, and to the division of nuclei which occurs in the 

 maturation of the reproductive elements in the higher forms of 

 animals and plants, 



(6.) Orbitolites complanata. Lamk. Figs. 41-51. 



My specimens of this species were collected from the reef at 

 Nukualofa, in Tonga, where it is very abundant. They were 

 preserved in 95 per cent, spirit, and have been examined by 

 means of section. 



I have also examined the fine series from Fiji in the Brady 

 Collection, the property of the University of Cambridge, 

 and a collection, in spirit, kindly placed at my disposal by 

 Dr S. J. HiCKSON, and obtained by him from the reef at 

 Talisse Island, to the north of Celebes. 



Before I left England my attention was called by the late 

 Mr H. B. Brady to this species, which he had obtained from 

 the reefs of the Fiji Islands, and especially to the desirability of 

 preserving specimens, with a view to following out their nuclear 

 history. The observations recorded in this paper are the out- 

 come of Brady's suggestion. 



The species is not, however, a good one for throwing light on 



