Cobb — Nematodes, mostly Australian and Fijian. 15 



Genus DIPLOGASTER, Schultze. 



The genus Diplogaster is composed of free-living forms, not marine, characterised 

 by the possession of a large pharynx armed with one or more teeth, and an 

 oesophagus with two well developed bulbs. If only one tooth is present it is 

 dorsal ; if more than one, then the larger may be dorsal and the others subsidiary, 

 or more often all may be small and basal. The average dimensions are indicated 



by the following formulae ; — W ".g \. — i- — n, in nun. jj^ — ^-s \- a- 2^ ^■""" The cuticle 



is commonly transversely striated, though apparently sometimes not, and moreover 

 presents longitudinal striations or perhaps more properly speaking wings, some- 

 times to the number of forty, of which those on the lateral fields are usually more 

 prominent, they being the only ones that continue far on the tail. Both these sorts 

 of markings are often resolvable into rows of dots or circles. The only hairs thus 

 far observed on the body are the cephalic setse seen on a few species, and those on 

 the male : these latter are doubtless tactile and partake more of the nature of papillae 

 ■than of ordinary hairs ; their arrangement and grouping will presently be described. 

 The papilla-like cephalic setae number four, or possibly six, and are always small and 

 very inconspicuous ; they are situated somewhat behind the outer border of the 

 truncate head. The lips, three in number, are sometimes single and sometimes 

 double, and are supplied with papillae, usually six, arranged around the mouth. The 

 entrance to the pharynx is usually wide and is often striated longitudinally. The 

 proportions of the pharynx vary much and serve very well to characterise the 

 different species ; sometimes the pharynx is shallow and cyathiform, and sometimes 

 long and triquetrous. The variation in the armature of the pharynx is no less 

 remarkable. Some species possess a single large dorsal tooth whose apex is directed 

 forward and situated near the centre of the pharynx, while other species possess but 

 a small or even rudimentary dorsal tooth ; yet other species seem to entirely lack a 

 dorsal tooth, and present instead a number of small teeth at the very base of the 

 pharynx. 



The oesophagus invariably possesses two well developed bulbs and sometimes 

 three : of these the spheroidal median is the most conspicuous, being supplied with 

 powerful radial muscles ; the more elongated cardiac bulb is second in importance and 

 is also supplied with well developed radial muscles ; the pharyngeal bulb is the least 

 conspicuous and is in fact nothing else than the expansion due to the presence of 

 muscles attached to the parts of the pharynx. Of the intermediate tubular parts of 

 the oesophagus, that between the pharynx and the median bulb is usually about half 

 as wide as the conoid neck and twice as wide as the other, — that between the median 

 and cardiac bulb, — and much less flexible. Some species possess a marked power 

 of contracting and extending the neck ; in the contracted state the intestine 



