THE LIFE HISTORY OF THE SCOLEX POLYMORPHUS 
OF THE WOODS HOLE REGION 
WINTERTON C. CURTIS 
From the Zoological Laboratory, University of Missouri 
THIRTEEN FIGURES 
CONTENTS 
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The normal occurrence of parasites in sand sharks taken at random....... 827 
The infection of sand sharks with the Scolex polymorphus................. 829 
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INTRODUCTION 
In attempting to determine the life cycle of Crossobothrium 
laciniatum, a cestode found in the sand shark, (Carcharias lit- 
toralis) of the Woods Hole region, attention was at once directed 
to the cestode larva known as the Scolex polymorphus, which 
seemed not unlikely to be the young of this species. The studies 
here described were begun in the hope that these two forms would 
prove to be a single species, since both are admirable for labo- 
ratory purposes and have been so used by students at the Marine 
Biological Laboratory for many years. It appears, however, 
that such a relationship does not exist; for theresultsof the exper- 
iments give strong, though perhaps not entirely conclusive, evi- 
dence that the Scolex polymorphus develops into the species 
Phoreiobothrium triloculatum (Linton) and show conclusively 
that it cannot be the young of Crossobothrium laciniatum. 
819 
JOURNAL OF MORPHOLOGY, VOL. 22, NO. 3 
