264 Macteay Memoria VoLume. 
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 
cesophagus 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 formule ge Ee tum pee a *3 tmm 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 setze seen on a few species, and those on 
the male: these latter are doubtless tactile and partake more of the nature of papillie 
than of ordinary hairs; their arrangement and grouping will presently be described. 
The papilla-like cephalic sete 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 papill, 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 cesophagus 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 
