456 Jlr. R. Kiikpatrick on the Slruclure of 



Note 8. — Tlie discovery of the primitive colonial Fora- 

 minifera will probably shed much light on the origin o£ 

 dimorphism (see J. J. Listei-, Phil. Trans. 1895, vol. 186, 

 p. 401, and F. W. Winter, ' Protistenkunde/ vol. x. 1907, 

 p. 1). The colonial habit gave way to the individual one 

 possibly owing either to the breaking otF of the buds or to 

 premature blocking up of tlie main gemmiparous stolon by 

 calcareous deposit. lu either case injury or damming u-p 

 might lead to endogenous division. The vegetatively formed 

 megalospherie shell would then have become a gamont 

 producing isogametes. Conjugating isogametes would form 

 a young microspheric agamont, which, by agamogony, would 

 form agametes, each of the latter becoming a young megalo- 

 spherie gamont. 



Winter writes (/. c. p. 106) : — " halte ich es fiir hojh-t 

 wahrscheinlich, dass Dichromasie und Dimorphismusderselbeii 

 alien Thalamophoren zukommt." I think this condition has 

 arisen owing to the repression of the original primitive 

 colonial habit giving rise to a simple sexual phase, the latter 

 recurring to a vegetative phase. la the text of this paper I 

 pointed out that in addition to the large buds formed on the 

 main axial stolon there were often little buds formed on any 

 part of a coiled shell. T think these little buds are almost 

 certainly megalospherie, but I am not at present certain. 



Note 9. — The great prevalence of an organism at a certain 

 epoch followed by its almost total disappearance constitutes a 

 very strange phenomenon in evolution. About the Eocene 

 epoch, for instance, the Numraulites flourished amazingly 

 and carpeted sea-floors over vast areas along a great belt 

 extending across the Eurasian continent from Spain to the 

 north-east corner of Asia. Nunnnulites were mostly iieavy 

 benthos organisms living in shallow seas, the latter probably 

 covering rising areas. At the very summit of a Himalayan 

 peak 19,000 feet above sea-level we find an Eocene sea-floor 

 composed mainly of Nummulites, the sea-bottom having been 

 gradually elevated by lateral thrust, (b^igures of this lime- 

 stone are given in the Natural History Museum Guide to the 

 Coral Gallery.) During the Cretaceous epoch and over 

 hundreds of millions of square miles of ocean at the present 

 day a surface- or plankton- Foraminiferan, viz. Globigerina, 

 has largely contributed to the formation of thick deposits of 

 Globigerijia-oozp. 



Note 10. — It seems to be legitimately within the limits of 

 the subject of this paper to consider why a primitive Rhizopod 



