72 MANUAL OF ZOOLOGY. 



system, is largely developed in many of the highest and largest of the types 

 of the Hyaline Foraminifera (such as Nummulina), and very specially so 

 in the ancient Eozoon, if this be rightly regarded as a Foraminifer. 



The recognition of a "nucleus" in many Foraminifera and 

 its probable presence in all renders it necessary to unite with 

 this group a number of fresh-water Rhizopods, which would 

 otherwise have to be placed with the Amazbea, and to which 

 we may, in a restricted sense, apply Hertwig's name of Thala- 

 mophora* The test in the forms in question is always one- 

 chambered, and in all except Diaphorophodon it is imperforate. 

 It may be smooth or sculptured, and in composition it may be 

 either membranous or chitinous, in some cases with adventi- 

 tious siliceous particles in addition. Both a nucleus and con- 

 tractile vacuoles are present in the protoplasm of the body ; 

 and the pseudopodia are long and filamentous or reticulated. 

 Of these simple " Reticularian " Rhizopods, Gromia(hg. 10, b) 

 is both a marine and a fresh-water form, and possesses a deli- 



Fig. 14. A colony of Micrygromia socialis^ showing the different members of the 

 colony united by their branching pseudopodia. Greatly enlarged. (After Hertwig.) 



cate membranous test, from a terminal aperture in which the 

 protoplasm gains the exterior. Microgromia (fig. 14) resembles 



* Under the name Thalamophora, Hertwig and Lesser include the true 

 Foraminifera, the monothalamous Rhizopods above alluded to (with " reti- 

 cularian " pseudopodia), and the Arcellina. The last of these, however, 

 on account of their blunt, lobose pseudopodia, are here placed in the order 

 of the Amoebea. 



