954 Macrteay Memorrat Vouume. 
only assert that they must impart to the wall of the pharynx an irregular sculpturing, 
doubtless well adapting it for mastication, for which purpose the exterior of the 
pharynx seems supplied with more abundant and more powerful muscles than in the 
other species. Doubtless these differences can be made the basis of a division of the 
genus into two natural subgenera. In those cases where the dorsal tooth is placed in 
the neighbourhood of the lips, [ have observed that the anterior walls of the pharynx, 
or the internal surface of the lips, are armed with large somewhat tooth-like almost 
backward-pointing processes, which I judge from their position (I have never seen 
them act) to be the antagonistics of the dorsal tooth. The lips and walls of the 
pharynx are always supplied with numerous and powerful muscles, concerning whose 
action Biitschli remarked that the head was often seen to contract longitudinally. 
The csophagus is very simple, being a tube half to two-thirds as wide as the 
neck, wider posteriorly than anteriorly, without bulbs of any sort, and separated from 
the intestine by a distinct but shallow constriction, which is sometimes double owing 
to the fact that the intestine is joined closely to the cardia for a short distance and 
then suddenly expands. The intestine is two-thirds to three-fourths as wide as the 
body and ends in a short and narrow rectum, only about two-thirds as long as the 
anal body-diameter. The intestine is usually thin-walled and is composed of cells 
whose granules are arranged so as to give rise to a tessellation, often of such a perfect 
and beautiful kind as to render these worms a most attractive spectacle. The nerve- 
ring surrounds the cesophagus squarely near the division between its anterior and 
middle third; before and behind the ring the usual ganglion cells occur. All the 
species are eyeless. The lateral fields are well developed, beg one-fifth to one-third 
as wide as the body. The lateral organs have remained until now undiscovered in 
all the species ; I find, however, that in ongzcaudatus they exist opposite the middle 
of the pharynx in the form of small transverse ellipsoidal openings. The ventral 
gland, too, has hitherto remained unseen, but in megalaimus and digiturus a pore 
and this pore has every appearance of being the 
exists Just behind the nerve-ring, 
outlet of the ventral gland. 
The tail varies in length from one-fiftieth to one-fifth of the length of the 
animal; when short it is conoid, and when long it is conoid in the anterior part and 
narrow and ecylindroid in the remaining part, being always slightly swollen at the 
terminus, which is rounded and gives exit to the secretions of the caudal glands, 
probably always three in number. 
In two species (dgz/avus and gymnolaimus) the female sexual apparatus is single, 
in all the others as yet made known it is double, the two parts being symmetrically 
reflexed, in spite of which fact, however, the projecting vulva is usually situated near 
the beginning of the posterior third of the body, a position in harmony with the 
