38 The Microscope. 



sion, the points at which the anterior branches enter the ventral part 

 of the pharyngeal vessels may have been misinterpreted. The 

 apparent arrangement is shown in the diagram (Fig. 3). 



The fluid of the body cavity seldom contains those freely float- 

 ing, granular corpuscles often so abundant within the body of other 

 aquatic worms. 



The nervous system can be studied satisfactorily only after sec- 

 tioning and staining. This must, therefore, be postponed. 



The worm's swimming movements are not performed by the 

 lateral undulations of the body so common with Pristina, Nais, and 

 other OligochiTeta. The labial cilia are here the chief organs of nata- 

 tion, and by their aid the worm advances evenly and smoothly 

 through the water. 



Although very many individuals have been examined, none have 

 been found sexually mature. The only form of reproduction 

 observed is by transverse fission, which takes place rapidly, a single 

 individual not rarely presenting evidences of two rej^roductive divi- 

 sions. 



In length the extended body may reach y^^ inch. The smallest 

 forms obsei-ved measured only about oV inch in length. 



III. 



PRISTINA FLAVIFRONS, SP. NOV. 



The body is for the most part colorless, or very pale brownish, 

 depressed sub-cylindrical, the articulations, of which there are from 

 thirty-seven to sixty-three, being quite uniform in width except near 

 the two extremities. The posterior or anal segment is narrowed, 

 tapering, and terminated by two rounded papillae, one on each side 

 of the anal aperture. These are hispid with short, stiff hairs (Fig- 

 4), as also is the entire body, but sparingly so, the short setae being 

 widely separated. 



The upper lip terminating the anterior extremity is somewhat 

 widened, and the pharyngeal segments immediately behind it are 

 slightly constricted. The lip is itself formed of a conspicuous, 

 rounded lobe on each side, with a deep depression separating them (Fig. 

 5), the long, soft and flexible proboscidiform process springing from 

 this central concavity, the entire region being hispid with many 

 short, stiff hairs. The lip measures from o}jj) to y4^„ inch in length 

 from the mouth, and, when the worm is observed in profile, the jDart 

 seems to be depressed, rounded iaferiorly, and slightly curved 

 upward so that it has, in longitudinal optic section, a concavo-convex 



