440 Dr. A. C. Stokes on some 



the infusorian's life-history. The form here referred to as 

 Z. acus undoubtedly belongs to the genus in which it is now 

 placed. Its ability to change its shape is not often exercised ; 

 but when the need arises the alteration is rapid and con- 

 spicuous. Its favourite haunt seems to be dead and partially 

 empty algal cells, where several of the species can usually be 

 found in the small pool affected by them. 



Anisonema emarginatum, sp. nov. (PI. XV. fig. 11.) 



Body suborbicular, depressed, the frontal border somewhat 

 narrowed, rounded, and centrally emarginate, the dorsal sur- 

 face convex, the ventral slightly concave ; flagella subequal 

 in size, the anterior or vibratile about twice as long as the 

 body, the trailing one slightly longer, both inserted near 

 together somewhat toward the right-hand side of the frontal 

 emargination ; contractile vesicle single, in the anterior body- 

 half near the right-hand margin ; nucleus not observed ; 

 endoplasm granular, enclosing numerous dark-bordered linear 

 corpuscles. Length of body y-gVir inch. 



Hob. Standing water, with Myriophyllum and other 

 aquatic plants. 



Entosiphon ovatus, sp. nov. (PI. XV. fig. 12.) 



Body ovate, somewhat depressed, a little less than twice as 

 long as wide, rounded posteriorly, narrowed anteriorly, and 

 slightly curved toward the ventral aspect, the frontal border 

 somewhat emarginate on the left-hand side, the cuticular 

 surface traversed by ten or twelve longitudinal sulci ; the 

 two flagella inserted near together on the left-hand side of 

 the pharyngeal aperture, the posterior or trailing one about 

 twice as long as the body, the anterior or vibratile not 

 exceeding the body in length ; pharyngeal tube protrusible, 

 extending backwards for fully four fifths of the entire length 

 of the body ; contractile vesicle single, near the left-hand 

 border of the frontal margin; nucleus spherical, near the 

 centre of the left-hand border. Reproduction by longitudinal 

 fission. Length of body -$1-$ to y^u inch. 



Hab. An infusion of dead leaves. 



Entosiphon sulcatus (£)uj.) , Stein, has the trailing flagellum 

 from two to three times as long as the body, the cuticular sulci 

 are but four or five, and the animalcule is very much smaller 

 than the form here described. The contractile vesicle has been 

 observed to become rosette-shaped in E. ovatus, as it has in 

 the form from European waters. Reproduction by longi- 



