ON THE LIFE-HISTORY OF THE FORAMINIFERA. 109 



megalosplieric (with a large central chamber), and microspheric 

 (with a small central chamber) respectively. 



What is the relation existing between these two forms of a 

 species ? Do the}' represent two sexes, or do they belong to 

 different generations ? I believe them to belong to different 

 generations. 



In what follows I have attemjjted to collect the more im- 

 portant evidence which bears on the life-history, and have 

 given an account of my own observations, which deal mainly 

 with two species : — Polystomella crispa (LiNN.), belonging to 

 the Perforate division of the group, and Orbitolites complanata, 

 Lamk., a representative of the Imperforata. 



The evidence will be presented under the following heads: — 



1. Previous contributions to the life-history of the Fora- 

 minifera. 



a. Observations on Reproduction and Dimorphism. 



b. The relation of Orbulina and Glohigerina. 



c. Observations on Nuclei. 



2. Observations on : — 



a. Polystomella crispa (Linn.). 



b. Orbitolites complanata, Lamk. 



c. Rotalia beccarii (Linn.). 



d. Truncatulina, d'Orb. 



e. Galcarina hispida, Brady. 



/. Cycloclypeus Carpenteri, Brady. 



3. Concluding Remarks. 



1, Previous Contributions to the Life-History 

 OF the Foraminifera. 



(a.) Observations on Reproduction and Dimorphism. 



In the year 1847, Gervais (12) brought before the Academie 

 des Sciences, an observation on some Triloculine Miliolidce, which 

 he had kept in sea water. Young individuals, consisting of a single 

 large chamber, with their shells already formed and capable of 

 sending out pseudopodia had appeared, in number about 100, 

 grouped about the orifice of a parent shell. He also states that 

 VOL. VI. 12 



