RHIZOPODA. 



181 



by holes, to shelter and protect the body (Foraminifera, 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 processes ; 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- 

 subs tan ce, 

 which is richly 

 granulated and 

 contains pig- 

 ment, contracts 

 slowly and 

 sends out at the 

 same time fine 

 thread -like rays 



(fig. 120), for FlG 120. Optical section through portion of the sarccde body of 



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" {Comptes rendus, 1835). 

 Ehrenberg, " Ubcr noch jetzt zahlreich lebende Thierarten der Kreidebildung 

 und den Organismus der Polythalamien " {AhJiandlung der Akad. zu Berlin, 

 1839). Max Sigm. Schultze, " Uber den Organismus der Polythalamien" 

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

 thometrcn" (1858). E. Haeckel, "Die Kadiolarien " (Eine Monographic. 

 Berlin. 1S62). 



ActinospJiaerium Eichhornii (after Hertwig and Lesser). N, nuclei 

 in the endosarc, from which the vacuolated ectosarc is clearly dis- 

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



visible. 



