MONONCHULTJS VENTRALIS 



195 



Intro, vilam staining shows the existence of a 

 dorso-ventral physiological differentiation in the 

 intestine of Mononchus longicaudatus. 



Renette. When this well-known mononch was 

 stained inlra vitam with trypan blue, the ampulla 

 and a short portion of the duct of the renette was 

 so distinctly seen as to leave almost no shadow of 

 doubt that this portion of the renette structure 

 is normal. I am inclined to think that the duct 

 soon takes a lateral turn, and possibly becomes 

 connected with the lateral field; thus far it has not 

 been possible to follow it more than a distance 



mrfi 

 p/i.. 



Fig. 1. Man- 

 chulus ventralis, 



/*' 



, 

 rl or til 



mil 



a very interesting 

 nema, found in 

 the Washington irltirtil 

 filter-beds. The 

 lateral fields are 

 shown with great 

 clearness; they fm 

 are made up of 

 about three rows 

 of cells, d ar lat, 

 each cell with an 

 egg-shaped nu- 

 cleus, nd ar lat. 

 The intestinal 

 nuclei, of about 

 the same size, are 

 shown darker. 

 Oesophageal 

 glands, sal, as in 

 Mononchus. The 

 small posterior 

 gonad, appar- 

 ently serving as 

 a testis, is shown 

 at 1st. Nearly the 

 whole of the tostis 

 is shown in the il- 

 lustration. The 

 spinneret is unus- 

 ually large, and 

 gives us for the 

 first time some 

 clue to the struc- w,,,.!,/ 

 ture and me- a 

 chanics of this 

 organ. The de- 

 tailsaremorefully 

 illustrated in Fig. 

 2. For abbrevia- 

 tions see p. 212. 



am of 



n-lm-liil 

 ////// m . 

 mr am . 



about equal to the radius of the nsck, so that the 

 size and structure of the glandular part remain 

 unknown. nlylcdl. 



MONONCHULUS gen. nov. 



Characters. Possessing the form and general 

 appearance of Mononchus, but having the spinneret 

 on the ventral side of the tail near the terminus, 

 and the pharynx smaller and narrower with thicker 

 walls, and with forward pointing onchi or teeth, of 

 which a subventral one dominates. The labial 

 papillae are smaller than is usual in Mononchus, in fact are barely visible. 





