BHIZOPODA. 



181 



by holes, to shelter and protect the body (Fora t ninif era, Radiolaria\ 

 In the Infusoria the sarcode body is bounded by an external mem- 

 brane, and is capable of quick and varied locomotion by means of the 

 movements of the cilia, hairs, bristles, etc., which it possesses. The 

 solid nourishing matter is taken in through a mouth, and the 

 remainder, after digestion, passes out through an anal aperture. 



CLASS I. RHIZOPODA.* 



Protozoa without external investing membrane, the parenchyma of 

 which protrudes and retracts jwocesses ; as a rule, a calcareous shell or 

 silicious skeleton is secreted. 



The body-substance of these animals, the shells of which were 

 described as Foraminifera or Polythalamia, long before their living 

 contents were 

 known, consists 

 of sarcode, and 

 is without any 

 boundary mem- 

 brane. 



The body- 

 substance, 

 which is richly 

 granulated and 

 contains p i g- 

 rnent, contracts 

 slowly and 

 sends out at the 

 same time fine 

 thread-like rays 

 (fig. 120), for 

 the most part 

 of a semi-fluid 

 consistency 



(pseudopodia) ; and these serve not only as a means of movement but 

 also for the reception of nourishment. The pseudopodia may, how- 



* Dujardin, "Observations sur les Rhizopodes" (Comjrft's triidu*. 1835). 

 Ehrenberg, ' Uber noch jetzt zahlreich lebende Thierarten der Kreidebihlung 

 und den Organismus der Polythalamien " (Alkdndluni/ (Jcr Aluid. zu Berlin, 

 1839). Max Sigm. Schultze, "Uber den Orga/iismus der Pulythalamien" 

 (Leipzig. 1854). Job. Miiller. '' Uber die Thalassicolen, Polycystinen und Acan- 

 thometren " (1858). E. Haeckel, "Die Radiolarien " (Eine Monographic. 

 Berlin. 1862). 



FIG. 120. Optical section through portion of the sarcode body of 

 Actinosplmerium Elchhoniii (after Hertwig and Lesser). N, nuclei 

 in the endosark, from which the vacuolated ectosark is clearly dis- 

 tinguishable. In the centre of the pseudopodia the axial thread is 

 visible. 



