THE SCOLEX POLYMORPHUS $33 
vive the treatment while other worms are not killed in the sharks 
which do survive. It should be remembered, however, that such 
non-survivors do not represent the weakest individuals in any 
lot, for the strongest were probably the ones which fought hardest 
when put in the holder and such very active sharks received 
rougher handling and perhaps they sometimes died from this 
cause. With these reservations, the specimens found soon after 
death and those killed when about to die, may be cited as showing 
the immediate effect of the drug upon the parasites. 
An important point, noted in some of the tables, is that about 
twenty-four hours after the dose of oil, that is, when the calomel 
was given, numbers of dead Crossobothria were squeezed from 
the anus as a shark was placed in the holder. Many entire 
worms of all sizes were thus obtained and these when placed in 
sea water slowly disintegrated, showing no signs of life, as they 
might have done if only stupefied by the oil. 
Of the five sharks here recorded, No. 1 was not in good condi- 
tion, though death did not seem near at hand, when it was killed 
the day after the oil was administered. It contained only dead 
C. laciniatum. Three days after the calomel was given the four 
remaining specimens were killed and examined, with the results 
which are shown in the table. They were all in good condition 
and the mucous membrane seemed quite normal. I may here 
state that my examinations of the spiral valves throughout this 
work have been most careful. In each case the outer wall was 
split longitudinally along one side and the cut continued down 
across the spiral folds to the opposite side. A similar cut was 
made across each fold along the middle of each half of the valve 
and the inner surface thus exposed as four parallel rows of trian- 
gular flaps, which were then examined one at a time under a lens. 
Where there was any such amount of chyme as to obscure the 
surface of the mucous membrane the valve was washed until 
clean and the washings examined in shallow dishes against a 
dark background. 
Table 2 shows the results in five sharks, which were given a 
heavier dose of the oil of male fern, and the calomel after an 
interval of forty-eight hours. After the dose of oil, shark No. 1 
