POLYTOMELLA CITRI, SP. NOV. 223 



reaching the periphery the single basal granule divides, the 

 rhizoplast dividing with it, to form the two basal granules. The 

 flagella do not develop until the organism is partly excysted. 



Excystment is ushered in by the dissolution of the cyst wall on 

 one side (Text Fig. Aa). Many stages of this thinning process 

 can be seen before the living cell comes in contact with the outside. 

 The first step in escaping from the cyst seems to be due to the 

 absorption of water, which swells the cell and causes it to protrude 

 through the dissolved opening. Complete freedom from the cyst 

 wall is attained by amoeboid movement of the newly formed 

 flagellate. Outgrowth of flagella begins just prior to flowing 

 away from the old wall. 



For periods varying from one to fifteen minutes the newly 

 excysted individual shows only amoeboid movement, without 

 regard for the polarization caused by the presence of flagella 

 (Text Fig. A e, f, g, h) . With the cessation of amreboid movement 

 they assume the typical form and swim off. 



DISCUSSION. 



Affinities. 



The presence of starch within the cell-body of Polytomella citri 

 and the typical Phytomonad symmetry are sufficient to establish 

 its position with the order Phytomonadina. Further, the fact 

 that the pellicle divides with the cell at fission places this organism 

 within the family Polyblepharididae. 



This family was suggested by Dangeard in 1887 to include, 

 at that time, Pyramimonas tetracynchus Schmarda, Chloraster 

 gyrans Ehrenberg, C. agilis Kent and Polyblepharides singularis 

 Dangeard. In 1905 Teodoresco placed Dnnaliella salina in this 

 group. This is a marine protozoan, as the name would indicate. 

 Griffith (1909) described Pyramimonas delicatulus, taken from a 

 pond in England. In 1910 Dangeard made another contribution 

 to the Polyblepharididae with his description of Stephanoptera 

 fabrece, a salt water form. This species is one of the largest of the 

 family, reaching 35 micra in length. Pyramimonas, 40 micra, 

 being the only one exceeding that size. All of the members of 

 this group possess the ability to change their shape to some extent 

 and Spermatozopsis exsultans (Korchikoff, 1913) has the dis- 



