99 



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NATURAL SCIENCE 



[July 



instance, Pullenia ohliqidloculata and Globicjcrina aequilatcralis ; on 

 the other hand, Pulvinulina menarclii and Gldbigcrina rubra appear 

 to be more abundant in the tropical Atlantic. 



The species inhabiting the north and south temperate regions, 

 and the species inhabiting the two polar regions, appear to be 

 nearly if not quite identical. 



The distribution of the dead shells of the pelagic Foraminifera 

 on the floor of the ocean corresponds exactly with the distribution 

 of the living specimens at the surface of the sea. It has sometimes 

 been urged that the dead shells of tropical species might be carried 

 a long way to the north or to the south by oceanic currents, but 

 this does not seem in any way to be the case ; the distribution of 

 the dead shells on the bottom does not appear to be much if any 



Fig. 3. — Cymbalopora (Tretomphalus) bulloides (d'Orbigny). a, large surface specimen ; 

 b, small (young) specimens from the same gathering ; c, distal face of the 

 balloon-like chamber, showing the entosolenian orifice, seated in a slight 

 depression. All magnified 60 diam. 



wider than that of the living specimens at the surface, and this 

 shows that the dead shells must reach the bottom a very short time 

 after the death of the organisms. The fact that the distribution of 

 these shells at the bottom of the ocean is governed by the surface 

 conditions is of itself almost conclusive proof that they live only at 

 the surface, for otherwise their distribution would be similar to 

 that of bottom-living, or benthos, species, which is wholly inde- 

 pendent of the temperature conditions prevailing at the surface of 

 the sea. Carpenter x and Brady 2 at one time held the view that 

 young individuals lived at the surface and adult ones at the bottom ; 

 in addition to the fact that no living specimen has ever been obtained 

 from the bottom, the above considerations with regard to distribu- 

 tion show that this view is not supported by any trustworthy obser- 

 vations. In the surface gatherings the young individuals are much 



1 Op. cit. 



- Op. cit. 



