1916] Wilson: On llir Llfr-llishn-,1 nf a Soil Aliinrha 267 



niiiiid ill tliis coiKlit ii)ii till' iii'xl iiiiirnin^r. in s|ii1i' of llic fad 1li:il llic 

 U-mpei-iiliirc was that of llic rDum by tliat tiiin.'. Al'trr tin- adililimi 

 of fri'sli sterile iiiediiiiii llie eliiiiips a1 niDiii temperature hl-dke ll|i and 

 the auuieliiis spread mit over the eover-jilass, hut if left a( low tempera- 

 ture there was no change, 



1. AImUI'IIOI.OGY 



The size of tlic flagellate, which is pyriform in shape with two eiiual 

 flagella slightly longer than the body and situated at the narrower 

 anterior hliint end (pi. 2'J, (ig, 10(1), is less lliaii thai of the ainoeha 

 because it is in a more rounded-up eonilition and it varies propdrtion- 

 ately as that of the trophozoite does. When (irst rorined a flagellate 

 is ovoid in shape and has its greatest cross-diameter almnt two-thirds 

 that of its longitudinal diameter (pi. 22, fig. !I7). hut when tin' pyri- 

 form shape, which is characteristic of older tlagellates, is reached the 

 greatest cross-diameter is less than half that of the longitudinal 

 diameter (pi. 22, fig. 106). After si;veral hours in the flagellate con- 

 dition it is not uncommon to find individuals with a knob of cytoplasm 

 projecting posteriorly (pi. 22, fig. 95). The size of this may increase 

 until only a neck of cytoplasm is left at the anterior (>iid. 



The eel()|)lasiii and elidoplasni are not dilferenl iai ed. Oecasionall.V 

 chromidia are formed in the cytoplasm. The contractile vacuole is 

 situated posterior to the nucleus, which is anterior near the base of the 

 flagella. The nucleus may (pi. 22, figs. 98, 102) or may not fi)l. 22, 

 fig. 95) have heavy peripheral chromatin. There is a plastin ediineetion, 

 the rhizoplast, fr(mi the karyosome to a darkly staining gi-aniile. the 

 blei)har()j)last, which is situated anteriorly al the |)eriphery ol' the 

 eytopla.sm. Extending from this are the two flagella. which with 

 Alexeieff 's triple stain are slightly rose-colored like th(> rhizophist and 

 the nuclear pla.stin. 



When heavy periphei'al ehromat in has been fduiid in the llagellates 

 there has always been the same condition in the material jninr to 

 enflagellation. As suggested before, the same thing is pmbably true of 

 the chromidia, that they would probably have formed nuclei of new 

 individuals had enflagellation not occurred. 



The description as given above for munonneleati- I'drms is ,dso true 

 for the multinucleate ones which are found in tlagellates produced from 

 multinucleate amoebas. In this ca.se there may be only two flagella 

 and these are connected with one nucleus (pi. 22, fig. 97) or rarely 

 there are found flagellates with two nuclei with two flagella related to 



