AMOKG SIMPLE SARCODE ORGANISMS. 387 



Fig. 2. 



Helio'phrys variabilis in the act of creeping. It has passed from a globular 

 form to that of an irregular disk. The pseudopodia have become divided. 

 e, rod-like granules of the outer hyaline layer. Other lettering as in preceding 

 fig. 1. (After Greeff.) 



Hertwig and Lesser, Eilhard Sehulze, and Archer have made 

 us acquainted with a large number of monothalamian Ehizopods of 

 fresh water. 



In almost all the freshwater forms the presence of a nucleus 

 can be demonstrated without difficulty ; and resting on the belief 

 universally entertained that the marine forms known in general 

 by the name of Foraminifera, whether monothalamian or polytha- 

 lamian, are, with one or two incompletely established exceptions, 

 destitute of a nucleus, Hertwig and Lesser saw in this difference 

 grounds for the association of the freshwater monothalamic Ehi- 

 zopods into a special group, to which they limited the name of 

 Monothalamia. 



The quite recent discovery, however, by Hertwig himself* and 

 by F. E. Schulzef, of a nucleus in several genera of Foraminifera, 

 and the great probability of its occurrence throughout the whole, 

 take away the only important structural difference between the 

 two groups, and render it necessary to embrace both in a single 



* " Bemerkungen zur Organisation und systematischen Stellung der Forami- 

 niferen," Jenaische Zeitschrift, 1876. 



t " Ueber den Kern der Foraminiferen," Archiv fiir mikr. Anat. 1876. 



33* 



