90 NOTES ON AVIAN ENTOZOA—LINTON. 
In the adult worm the body is rather stout and dark colored, due to 
the contents of the intestine. Those found in the wsophagus were 
smaller and lighter colored than those found in the stomach. More- 
over, they were attached to the mucous membrane of their host, leav- 
ing a small round pit when removed. The body is of nearly uniform 
size throughout, tapering a little more at the anterior than at the pos- 
terior end. The head is characterized by having a triangular spine- 
like interlobe in the intervals between the three proper lobes of the 
- head (Fig. 6). Papillae were observed near the anterior end of some 
(Fig. 6). They appeared to be more common on the females than on 
the males, but are variable in number and frequently altogether ab- 
sent. 
The cesophagus is slender and rather short. There is a short diver- 
ticulum beyond its union with the intestine; the latter also extends 
forward of the union with the cesophagus for a short distance as a 
blind sae. 
In both the Guaymas and the Yellowstone specimens the females. 
considerably outnumbered the males. The sexes are readily dis- 
tinguished. The posterior end of the males is usually curved sharply 
and is provided with two long filiform spicules which, when fully ex- 
tended, may curve almost into a circle. The spicules are of unequal 
length. When the spicules are not visible for any reason the males 
may still usually be recognized by the flattened surface near the pos- 
terior end, which ordinarily presents a grooved appearance between 
the retractor muscles of the spicules. 
Bodies of the females frequently swollen in the region of the repro- 
ductive aperture, which is placed about the anterior third. This aper- 
ture in one of the adult specimens measured 0.75 millimeter in length 
and 1.25 millimeters in a direction transverse to the axis of the body. 
The posterior end of the female is cylindrical, pointed, and not re- 
curved, as in the male. The ova measured 0.06 millimeter in diameter, 
the shell of the same being 0.005 millimeter thick. Some were observed 
in which segmentation had begun; both morule and gastrule were 
noticed. This was in the eggs from a Guaymas specimen. 
My observations on the anal papillse were made on a single adult 
male. Their disposition is shown in the diagram, in which the precise 
relative distances from each other are perhaps not exactly shown. 
There are, as is shown in the sketch (Fig. 10) six pairs of post-anal 
papillz, symmetrically arranged. The four anterior of these pairs are 
distinguished by having a common disk. ‘The two posterior pairs are 
without disks and the papillz in each pair slightly removed from each 
other. The latter are smaller than the other pairs, and of the others 
the anterior pairs are the larger. The pre-anal papillae begin opposite 
the anal aperture and extend in symmetrical rows along each side. 
They are a little closer together near the posterior end of the rows for 
about eight papille. In the specimen examined there were about 
twenty-six pre-anal papillz in each row. 
