PROTOZOA 63 



In the conical front region on which the first set of flagella stand, the 

 rhizoplasts and basal granules are merged to form converging strands 

 with which the flagella are connected . At division this conical apparatus 

 acts as a division centre, dividing first and forming the spindle between 

 Its halves as they separate. Possibly It does so in virtue of a concealed 

 centrlole. Trichonympha is symbiotic with termites, In whose gut It lives 

 (p. 412). The termite devours wood but Is unable Itself to digest It. 

 The digestion Is performed by the protozoon, which obtains In return 

 food and lodging. Wood particles are contained In the endoplasm of the 

 hinder part of the body of Trichonympha, Into which they are Ingested 

 by the cupplng-ln of this region under the action of the myonemes of 

 the fore part. 



Class SARCODINA (RHIZOPODA) 



Protozoa which in the principal phase are amoeboid, without flagella ; 

 are usually not parasitic ; have no meganucleus ; and, though they may 

 have a phase of sporulation, do not form large numbers of spores after 

 syngamy. 



With the exception of the Amoebina and Foramlnlfera, which are 

 undoubtedly closely related, the orders of this class have much less 

 affinity with one another than have those of the Mastigophora. In 

 all of them flagellate young and gametes are common. 



Order AMOEBINA 

 Sarcodina which have no shell, skeleton, or central capsule; whose 

 pseudopodia never form a reticulum and are usually lobose ; and whose 

 ectoplasm is never vacuolated. 



Thus defined, the group excludes forms such as Arcella which 

 differ from Its members practically only in the possession of a shell. 

 These forms, however, are also connected with the typical Foraml- 

 nlfera by Intermediates (as Lieberkiihnia and Allogromia). There is, 

 indeed, a continuous series from naked amoebae to such foramlnlfera 

 as Polystomella, and the drawing of a boundary line between the 

 groups of which they are typical Is a matter of convenience. 



Naegleria (Fig. 53). Small amoebae which live in various foul 

 infusions ; possess a contractile vacuole ; and in certain conditions pass 

 Into a biflagellate phase. Naegleria is placed here rather than among 

 the Rhizomastigina because it Is most often in the non-flagellate con- 

 dition. Its flagellate phase, though fully grown, is not known to per- 

 form reproduction, and the general features of the amoeboid phase 

 are those of the amoebina of the Umax group, most of whose members 

 appear to have no flagellate phase. These organisms form one or two 



