54 SYNOPTIC COLLECTION. 



as they were whirled along by the cilia of the disc. Many 

 of the particles are seen passing downward into the tube 

 at the end of which they have formed a pellet that be- 

 comes surrounded by a jelly-like substance. The arrows 

 within the body show the definite course of the pellets in 

 the body cavity. The nourishment having been separated 

 from the food, the excrement is ejected at the swelling 

 which rises temporarily on the ventral side of the poste- 

 rior part of the body, as seen on the left of the drawing. 

 The contractile vesicle according to Kent is normally 

 spherical, as represented in the posterior part of the 

 body, but under pressure it assumes the condition seen 

 in the anterior portion of the body extending outward in 

 the form of ray-like continuations. The nucleus, colored 

 yellow in the drawing, is the long tubular organ with 

 three enlargements just in front of the posterior spherical 

 contractile vesicle. E. Ray Lankester 1 has shown in 

 Paramoecium aurelia Miill. 2 a marked differentiation of the 

 protoplasm into two well defined parts. The outer por- 

 tion is bounded by a cuticle that is pierced by holes 

 through which pass the cilia. Just under the cuticle are 

 little sacs or tricocysts, each one containing a thread 

 which can be thrown out, and which is helpful as a defen- 

 sive and probably as an offensive organ. Attached to 

 one side of the nucleus is the apparently small nucleus, 

 the paranucleus, 3 which probably arises from the nucleus. 

 The investigations .of Balbiani and others have shown 

 that the reproductive phenomena of Paramoecium and the 

 Infusoria generally are more complicated than those of 

 the Rhizopods or the Flagellata. Temporary conjuga- 

 tion takes place between the zoons of Paramoecium and 



1 Encycl. Brit., ed. 9, XIX, 1885. 



2 The Paramoecium catt datum of Ehrenberg is probably a variety 

 of the P. aurelia of Miiller. 



3 The paranuclei are sometimes called nucleoli. but objectionably, 

 since the paranucleus has nothing to do with the nucleolus of a 

 typical cell (E. Ray Lankester, Encycl. Brit., ed. 9, XIX, 1885). 



