74 



THE INVERTEBRATA 



Diffiugia (Fig. 60). Shell of sand grains, etc., united by organic 

 secretion, pear- or vase-shaped; pseudopodia lobose; one or two 

 nuclei and a chromidium present. Gas vacuoles sometimes formed. 

 In fresh waters. 



Euglypha (Figs. 7, 58). Shell resembling that of Difflugia but 

 formed of siliceous plates secreted by the animal; pseudopodia filose. 

 In fresh waters. 



Trichosphaerium. Flat, encrusting forms, with a jelly coat; finger- 

 like pseudopodia protruding through separate openings in the coat; 

 and numerous nuclei. Reproduction alternately by escape of amoe- 

 bulae and of biflagellate isogametes ; but both generations can perform 

 plasmotomy. Marine. 



sh. 



Fig. 60. Fig. 61. 



Fig. 60. Difflugia urceolata, x 100. After Leidy. sh. shell composed of 

 particles of sand containing body of the animal ; ps. pseudopodia. 



Fig. 61. Lieberkuhnia wagneri. After Verworn. 



Lieberkiihnia (Fig. 61). Shell thin, flexible, egg-shaped, with 

 mouth directed to one side; pseudopodia reticulate. Shell divided at 

 binary fission. Marine and in fresh waters. 



Suborder POLYTHALAMIA 



Foraminifera, nearly always of marine habitat; usually with a shell 

 of several chambers, which is most often calcareous, but sometimes 

 with one chamber or no shell ; whose pseudopodia are reticulate ; and 

 whose protoplasm extends as a layer over the shell. 



The external layer of protoplasm can be withdrawn into the shell. 



