6 Cobb -Nematodes, mostly Australian and Fijian. 



unusually great length of the oesophagus, which seldom occupies in adults less than 

 one-fourth the length of the body. The eggs are usually eUipsoidal and somewhat 

 longer than the body is wide ; they are generally deposited before segmentation 

 begins. The reflexed part of the ovaries is usually short, seldom reaching more than 

 half-way back to the vulva. 



The tail end of the male generally resembles that of his mate in form, but differs in 

 the presence of numerous low broad papillae, of which a ventral row of a dozen or more 

 closely approximated ones are found in front of the anus, while several others are found 

 scattered over the tail. Each of the two equal slender spicula is generally supplied 

 near the middle of the shaft with an additional piece of chitin which doubtless serves 

 to render it less flexible. The accessory piece is double and surrounds the spicula. 



"While the genus Mononchus is one easily recognised and defined, it is one whose 

 affinities have been somewhat misunderstood. It does not stand in such close 

 relationship to Oncholaimus as was formerly supposed. The structure of the pharynx 

 which was thought to give it that relationship is now more clearly understood, and is 

 seen to present a superficial rather than a real resemblance to the pharynx of 

 Oncholaimus. The structure of the lips is very different in the two genera, those of 

 Mononchus being thick, armed with a double row of prominent papillae and not 

 accompanied by cephalic setae, while those of Oncholaimus are thin, lack at any rate 

 conspicuous papillae and are always accompanied by setae. The inner walls of the 

 pharyngeal cavity of Mononchus are moreover armed with rasp-like or file-like 

 roughnesses, not seen in Oncholaimus. Leaving the pharynx we come to other very 

 striking differences. For instance, no ventral gland has yet been demonstrated in 

 Mononchus, although it probably exists, while it is never absent and is usually 

 conspicuous in Oncholaimus ; then, too, the nerve-ring in the former genus is always 

 considerably in front of the middle of the oesophagus, while in the latter it is near the 

 middle or behind it; again the male copulatory organs of the two genera differ widely 

 from each other, and this brings to mind another difference, namely, the extreme 

 rarity of males in one case and the comparative abundance in the other ; Oncholaimus 

 is marine, while Mononchus lives in soils and on the surface of land plants ; the 

 peculiar organ seen in the females of Oncholaimus has not been met with in Mononchus. 

 These differences and others seem to me to show that only a somewhat remote 

 relationship exists between these two genera. 



I am of opinion that the worms belonging to this genus can by no means be 

 termed harmless to vegetation. My opinion is based on data collected during several 

 years and is therefore worthy of the attention of vegetable pathologists. 



Mononchus is distributed all over the world. I have myself examined specimens 

 from North America, Europe, tropical Asia, Australia and Fiji. The species do not 



