110 Dr. A. C. Stokes on some 



nation is needed to further suggest that this form is connectant 

 or transitional between the Holotvicha and the Peritricha, the 

 presence of cilia on the posterior body region being alone needed 

 to relegate the creature to the former order, and the develop- 

 ment of distinctly differentiated adoral cilia, in addition to the 

 cuticular series now existing, being only necessary to admit 

 it as an undoubted member of the Peritricha, Its peculiar 

 springing or leaping movements call to mind the similar 

 saltatory efforts of llalteria. Occasionally a depression is 

 formed around the body at a short distance from the posterior 

 extremity, when the little creature not remotely resembles an 

 acorn in its cup, an appearance that suggested tlie generic 

 name. 



Balayntozoon agile^ sp. nov. (PI. I. fig. 19.) 



Body conical or subjjyriform, less than twice as long as 

 broad, widest and truncate posteriorly, tlience tapering to the 

 frontal border ; the anterior two thirds only of the cuticular 

 surface clothed with long adcurved cilia ; posterior terminal 

 seta subequal to the body in length, its distal extremity 

 usually curved ; oral aperture apical ; anal opening not ob- 

 served ; contractile vesicle single, sjjherical, situated near one 

 side of the posterior border ; nucleus small, subspherical, 

 placed near the centre of one lateral margin ; endoplasra 

 colourless, often granular posteriorly, and enclosing coloured 

 food particles ; movements rotatory on the longitudinal axis, 

 with frequent and violent lateral leaps. Length of body y-g-Vij 

 inch. 



Hah. Standing water, with Sphaijnum. Reproduction by 

 transverse fission. 



The cuticular cilia appear to be disposed in distinct parallel 

 circles, not in the spirals so common to the Peritriclia. 

 Neither is there any sign of tlie peritrichous arrangement of 

 an anterior or adoral ciliary wreath where one arm of the 

 spiral descends into an oral fossa, since no fossa exists here, 

 the oral aperture being a minute orifice followed by a short 

 but distinctly visible pharyngeal passage. The cilia are com- 

 paratively long and are usually curved towards the frontal 

 extremity. 



The movements, in addition to the sudden lateral leaps, 

 which are presumably caused by the action of the postero- 

 terminal seta, are rapid and erratic. Eeproduction is by 

 transverse fission, the springing seta being developed from 

 the posterior portion of the anterior moiety, and projecting 

 obliquely from and beyond the deepening constriction for a 

 long time before the final separation of the animalcule. 



