PROTOZOA : FORAMINIFERA. 59 



believes that the coceospheres are most probably their " spor- 

 angia," Upon this view the term " coccoliths " would be re- 

 stricted to the fossil forms. 



Distribution of Foraminifera in Space. — The jForamim- 

 fera are mostly marine, and are found in almost all seas, though 

 more abundantly in those of the warmer parts of the globe. 

 It is concluded by Dr Carpenter that "the foraminiferous 

 fau7ia of our own seas probably presents a greater range of 

 variety than existed at any preceding period ; but there is no 

 indication of any tendency fo elevation towards a higher type." 

 One of the most remarkable facts about their distribution at 

 the present day, is the existence of a deposit at great depths 

 in the Atlantic, but only in areas traversed by heated currents, 

 formed almost entirely of the shells of Foraminifera, and very 

 closely resembling chalk. It has further been quite recently 

 established that there coexist with these Foraminifera various 

 animals of a higher grade, some of which closely resemble, or 

 are even specifically inseparable from, well-known Cretaceous 

 species. There is therefore some reason to conclude that the 

 bottom of the sea at great depths is peopled at the present day 

 by a fauna which is very closely allied to that of the Chalk. 

 Most living Foraminifera are very minute, but some of the 

 extinct forms attained a size of as much as three inches in 

 circumference {e.g., the NummuUte, fig. 5), and spheres of 

 Parkeria may attain a circumference of nearly four inches. 

 Some forms may be obtained adhering to the roots of tangle 

 at or near low-water mark, but they are mostly to be dredged 

 from tolerably deep water. They have been found, in fact, in 

 great abundance in the deepest parts of the ocean which have 

 as yet been examined by the dredge — at a depth, namely, of 

 nearly three miles. 



Distribution of Foraminifera in Time. — Remains of 

 Foraminifera have been found in Palseozoic, Mesozoic, and 

 Kainozoic formations. In the oldest stratified rocks with 

 which we are acquainted — viz., the Laurentian rocks of Canada 

 — there occurs a singular body which has been described as the 

 remains of a gigantic Foraminifer, under the name of Eozoon 

 Canadense. If truly organic, as is doubted by some, it is the 

 oldest fossil as yet discovered. It appears to have grown in 

 reef-like masses resembling the sessile patches of Polytrema* 



* Polytrema is a little branched coral-like Foraminifer, composed of a 

 calcareous test forming a number of irregular chambers, which communicate 

 with one another by wide orifices, and are filled with colourless sarcode. 

 The walls of the chambers are also penetrated by an extensive system of 

 capillary canals. 



