58 



ZOOLOGY 



SEPT. 



alternation of generations (p 



FIG. 40. Actinophrys sol. a. axial 

 filaments of pseudopods ; n. nucleus ; 

 p. pseudopod. (From Lang's Com- 

 parative Anatomy, after Grenacher.) 



In the Atlantic, large areas of 

 gray mud called Globigerina 

 Globigerinae contained in it. 



41) the megaspheric form alter- 

 nating with the microspheric, and 

 the latter being developed as a 

 result of a process of copulation, 

 the former without it (alternation 

 of sexual and asexual generations). 



Distribution. Gromia, Micro- 

 gromia, and a few other forms are 

 found in fresh water : one species 

 has been found in damp earth, but 

 the great majority of the Fora- 

 minifera are marine, some being 

 pelagic, i.e. occurring at or near 

 the surface of the ocean, others 

 abyssal, i.e. living at great depths. 



the sea-bottom are covered with a 

 -ooze from the vast number of 



FIG. 41. Actinpspliaerium eichhornii. A, the entire organism ; B, a small portion 

 highly magnified ; chr. chromatophore ; cort. cortex ; c. rac. contractile vacuole ; med. 

 medulla ; nu. nuclei. (From Butschli's Protozoa, after Hertwig and Lesser.) 



From the palaeontological point of view, the Foraminifera are a 

 very important group. Eemains of their shells occur in various 

 formations from the Silurian period to the present day, certain 



