448 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
I was much surprised to find this form swimming about freely in the water; its mouthless 
condition showed it to belong to the family of parasites, the Opaliniclie. As the name indicates, how- 
ever, this species is an ectoparasite upon the gills, and Stein gave the name branchiarurn to a fresh- 
water form parasitic upon Gannmcirus pulex. The Woods Hole form is so strikingly similar to the figure 
of G. branchiarurn that, although the name was given to a fresh- water form, it obviously applies to this 
marine variety. One important difference is the presence of only one contractile vacuole in the 
marine form. 
Key to families of Heterotrichida. 
Cilia cover the body 1 
Cilia reduced to certain localized areas 2 
1. Polytrichina. 
a. The mouth terminates a long peristomial furrow having an adoral zone along the entire left 
edge Family Plagiotomiclx 
b. Peristomial area a broad triangular area ending in mouth Family Bursaridx 
c. Peristomial depression short; limited to the anterior end; its plane at right angles to the long axis 
of body; surface of peristome striated and ciliated; no undulating membranes Family Stentoridx 
2. Oligotrichina. 
а. Peristome without cilia; cilia limited to one or more girdles about body .Family Halteriidx 
One marine genus * Slrombidmm, p. 449 
б. Thecate forms; the body is attached by a stalk to the cup; within the adoral zone is a ring of 
cilia Family Tinlinnidx 
c. The peristomial depression is deep and funnel-like; cuticle thick, with posterior spine-like proc- 
esses Family Ophryoscolecidse 
Key to the marine genera of Plagiotomidx. 
Diagnostic characters: The peristome is a narrow furrow which begins, as a rule, close to the anterior end and runs 
backward along the ventral side, to the mouth, which is usually placed between the middle of the body and the posterior 
end. A well-developed adoral zone stretches along the left side of the peristome, and is usually straight. 
1. Body cylindrical; size medium; peristome long and turns sharply to the left at the extremity Genus Metopus 
2. No torsion in the peristome; undulating membrane is confined to the posterior part of peristome Genus Blepharisma 
3. No peristomial torsion; body highly contractile; no undulating membrane Genus Spiroslomum 
Key to the mar ine genera of Bursaridx. 
Diagnostic characters: The body is usually short and pocket-like, but may be elongate. The chief characteristic is the 
peristome, which is not a furrow, but a broad triangular area deeply insunk and ending in a point at the mouth. The 
adoral zone is usually confined to the left peristome edge, or it may cross over to the right anterior edge. 
1. The anterior half of the body tapers to nearly a point in front; the peristome is narrowest at the apex; 
the mouth is the entire peristome base Genus Balantidium 
2. The anterior end does not taper; the peristome is widest at the end of the body; the mouth is clearly 
defined Genus* Condylostoma, p. 448 
Genus CONDYLOSTOMA ( KONDYLOSTOMA Bory de St. Vincent 1824) Dujardin ’41. 
(Dujardin ’41; Claparede & Lachmann ’58; Stein ’59, ’67; Cohn ’66; Quennerstedt ’67; Wrzesniowski ’70; 
Btitschli ’76, ’88; Kent ’81; Maupas ’83; Shevyakov ’96.) 
Colorless and more or less flexible animals of medium size. The general form is elongate and 
cylindrical or somewhat smaller anteriorly. The posterior end is broadly rounded, the anterior end 
somewhat truncate and oblique. The peristome is broad and triangular, the base of the triangle being 
the entire anterior end of the body. The entire length of the peristome is one-fourth or less of the 
body length. The mouth is large and placed at the apex of the peristomial triangle and opens into 
a comparatively small oesophagus. The right edge of the peristome is lamellate and bears a clearly 
defined undulating membrane. The adoral zone is well developed upon the left edge of the peristome, 
from which it passes around anteriorly to the right edge. The surface of the peristome is free from 
cilia, but the rest of the body is uniformly coated with small active cilia. Contractile vacuoles are 
not safely determined. Btitschli thinks there is probably one terminal vacuole, but some observers 
deny this (e. g. Maupas). Others describe them on the dorsal side of the posterior end (Quennerstedt). 
The macronucleus is long and beaded and placed upon the right side. Micronuclei are numerous and 
scattered along the macronucleus. The anus is terminal and dorsal. Food consists of large and small 
particles. Movement rapid, free swimming, alternating with resting periods; in some cases an undu- 
lating or wriggling movement is seen, showing clearly the flexibility of the body. Fresh and salt water. 
