LIFE HISTORY OF A TROUT PARASITE. 
345 
Head, in lateral view of body, elongated, wedge-shaped (resembling exactly some 
heads of D. cordiceps from cysts in Salino myMss, which I have collected), largest at 
base, tapering slightly towards apex, narrower than neck, except immediately at base, 
where it is of same breadth as neck (Fig. 17). In marginal view of body the head is 
broader than the neck and snbsagittate (Fig. 18). Bothria lateral, lips rather thin and 
flexible. 
Millimeters. 
Length of head 2. 00 
Diameter, corresponding to marginal diameter of body 80 
Diameter, corresponding to lateral diameter of body 55 
Diameter of neck, lateral 80 
Diameter of neck, marginal 60 
ileck, immediately behind head, crossed by flne lines which, less than 2 milli- 
meters back of the head, divide the body into short but evident segments. The body 
increases in breadth slowly and uniformly, and at a distance of 30 millimeters from the 
head is 2.5 millimeters broad; at 60 millimeters, 4.5 millimeters broad, at which point 
the segments are about 0.5 millimeter in length. At about 40 millimeters from the 
head a faint, darkish, median line is discernible, which becomes darker and more evi- 
dent farther back. With a lens this median line is seen, in maturing segments, to be 
occupied by the reproductive apertures. The dark color is due to clusters of ova. 
The reproductive apertures are lateral, near the median line of the strobile, not far 
from the anterior edge of each segment, and on but one of the lateral faces of the 
strobile. From some of the apertures a short, blunt cirrus was seen protruding. 
For about 15 centimeters the strobile was thickish with entire margins, then for 
about 10 centimeters it was characterized by remarkably ruffled margins. This was 
in the widest part of the strobile. The segments were here much crowded. The 
strobile in this ruffled portion is also thickish, at least when it is compared with the 
succeeding portions. At this point the breadth is 7.5 millimeters, the broadest part of 
the strobile; the length of the segments, 0.34 millimeter ; the thickness about 1 milli- 
meter (Fig. 21). 
Beyond the ruffled portion, the strobile becomes flatter, much thinner, and decreases 
in breadth, while the segments become squarish. A characteristic scalloimd margin 
is produced (Fig. 23) by the frequently concave margins of segments and their promi- 
nent posterior edges. Near the posterior end of this fragment the segments had the 
following dimensions : Length, 2 millimeters; breadth, 4.5 millimeters ; thickness, 0.5 
millimeter or less. The ruffling of the margin of the median portion of the strobile 
may be due in part to the action of the alcohol. 
Another fragment, smaller in most of its dimensions than the above, presents some 
characters which should be noted. The entire length is 22 centimeters. The head is 
somewhat contracted longitudinally and is bluntly rounded in front. 
Millimeters. 
Length of head 1. 00 
Diameter of head, corresponding to marginal diameter of neck 0. 75 
Diameter of head, corresponding to lateral diameter of neck.... 0.75 
Marginal diameter of neck 0. 50 
Lateral diameter of neck 0. 75 
Neck almost immediately crossed by flne transverse striae, which give rise to 
distinct segments 5 or 6 millimeters back of the head, where they are one eighth of a 
