CONJUGATION IN BLEPHARISMA UNDULANS 669 



The nuclear differences are less important and have no specific 

 value as will be shown in the following pages. 



The organism, with which we are dealing in the present paper, 

 belongs to Stein's second species, Blepharisma undulans, with 

 the following characters: Size of longest individual observed 

 220m, shortest, 70^1. Color variable, from deep purple violet 

 to light rose, or perfectly colorless. Form variable according 

 to the condition of the posterior end, but is usually sufficiently 

 striking to be easily identified. It is somewhat lancet formed, 

 thickest in the middle and tapering towards the two ends (fig. 1). 

 The posterior end is usually broader than the anterior, and, save 

 in exceptional cases, does not come to a point but ends in a broadly 

 rounded surface. The anterior end, on the contrary, comes to 

 a rounded point in which three lines converge, the left margin 

 of the body, and the right and left borders of the peristome. 

 The peristome is a deep cleft on the right ventral side of the 

 body running and deepening slightly in an oblique direction 

 towards the left (fig. 2). The adoral zone, composed of long 

 slightly tapering membranelles, begins on the left of the anterior 

 tip and is continued posteriorly on the left peristome margin to 

 the mouth where it sinks below the surface with the peristome. 

 An undulating membrane arises close to the mouth deep in 

 the peristome and extends along the right margin of the peri- 

 stome and towards the anterior end, stopping half way between 

 the mouth and the end. It is about one-half as broad as long 

 and extends well beyond the surface of the body so that it can 

 be seen distinctly with the lower powers of the microscope (fig. 3) . 

 A second undulating membrane, much smaller and very diffi- 

 cult to see, even with the highest powers, extends from the 

 mouth along the left margin of the peristome inside of the adoral 

 zone, for a distance equal to about half that of the right mem- 

 brane. This is probably the same thing as the 'Up' described 

 by Anigstein in B. clarissima. Unlike B. lateritia the body, 

 as a rule, is only slightly if at all compressed, but at times it is 

 definitely flattened especially in the oral region. The body 

 stripings are distinct and from nine to sixteen in number. The 

 macronucleus is single, double or multiple, and free micro- 



