THE SCOLEX POLYMORPHUS &29 
THE INFECTION OF SAND SHARKS WITH THE SCOLEX 
POLYMORPHUS 
The first attempt at infection of the sand sharks with the Scolex 
polymorphus was made with fish which had been held without 
food for a period of three weeks, a treatment which Monticelli 
(83)found effective in ridding aspecies of Torpedo of its Callioboth- 
rium. In all, eleven fish were so treated and each was then given 
all the larvae obtainable from twelve squeteague, a dose which 
was estimated at not less than five hundred larvae for each shark. 
Each fish was fed at the time of the infection and in the three 
weeks after infection, during which they remained alive, each was 
fed four times. For food, the flesh of the squeteague was used, 
an amount about equal to one-third, or one-half the bulk of a good 
sized fish being used at a feeding; my guide in this matter being 
the size of the pieces of food commonly found in the stomachs 
of recently captured sharks, which had fed under natural con- 
ditions. Judging from the rate of digestion, as observed on sey- 
eral occasions, this amount of food was unnecessarily large. 
Such an amount once a week would be ample for sharks in cap- 
tivity. Moreover, the choice of food was not good; for one may 
be introducing almost any kind of a cestode larva by feeding the 
flesh of a teleost fish. In using for infection sharks which had 
not received any treatment, other than the three weeks’ starving 
above mentioned, I was, of course, aware that one might expect 
each one of them to contain the normal infection of C. laciniatum. 
It seemed, however, that if the S. polymorphus from the sque- 
teague did represent the larval form of Crossobothrium, it would 
develop readily in its normal host, and that the introduction of 
a very large amount of infection would perhaps give the fish 
thus treated so many young worms all the same size, as to show 
that they could only have come from the larvae introduced by 
the experimental infection. 
Three weeks after the infection these eleven sharks were killed 
and their digestive tracts carefully examined. Each contained 
adult specimens of C. laciniatum in numbers sufficient to indicate 
that all the sharks had their normal complement of parasites and 
