42-4 University of California Publications in Zoology [Vol. 19 



microdissection experiments, I should subdivide the seven frontal cirri 

 into an anterior group of three and a more posterior group of four. 

 Accordingly, these will hereinafter be referred to as the "group of 

 three" and the "group of four" frontal cirri. 



The ciliary composition of the cirri of various Euplotes is a well 

 established fact. The component cilia with their basal granules have 

 been described for the cirri of E. vannus by Minkiewiez (1901), of 

 E. harpa by Prowazek (1902), of E. urorcesteri by Griffin (1910), and 

 of E. patella- by Yocom (1918). This feature of a cirrus may be 

 readily demonstrated in a shallow hanging drop by means of a V- 

 shaped dissection needle. Here a detached cirrus may be pushed to 

 I hi' edge of the hanging drop for greater surface tension and gently 

 rolled to and fro between the needle and cover-slip. Soon the cirrus 

 splits into loose bundles of its numerous cilia. But this method reveals 

 other features : the cilia are embedded in a gelatinous matrix that is 

 highly viscous, as may be seen by pushing the bundles about with the 

 needle. These remain attached at one or several places even after 

 rather rough handling. They frequently adhere to the needle and so 

 may be pulled a considerable distance through the water. Upon ex- 

 posure to the water for a few minutes, the cilia of the bundles further 

 separate and show adhering to their sides minute globules of the 

 coagulated matrix. The question here arises whether this coagulation 

 of the viscous, hyaline matrix may not account for the extreme rigidity 

 that overtakes the cirrus soon after its detachment, when it may be 

 pushed about and even beyond the margin of the shallow hanging 

 drop without any apparent bending. Furthermore, after examining 

 numbers of these cirri by the above method, one becomes rather con- 

 vinced that the matrix-cilia complex is invested with an extremel.v 

 thin, structureless membrane that is fairly tough but very flexible. I 

 have not been fully satisfied about this structure since 1 have net 

 clearly seen it apart from its enclosure. This final evidence may later 

 appear. However, if present, the membrane rapidly dissolves from a 

 recently detached cirrus, which then splits into its component cilia. 



Except the anal cirri, all are round at their base and gently taper 

 to a rather sharp point. The two right marginal cirri are fimbriated 

 (Yocom. 1918). Not infrequently the second and third (numbering 

 from left to right) anal cirri are also fimbriated. The shape of the 

 base of the anal cirri differs considerably from the others. Figures 

 19 and 18 show the comparative dorso-ventral width and lateral thick- 

 ness of an anal cirrus base, the former being six to eight microns and 

 the latter about three microns. 



