PLATE I.

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1. Ovum of S. spindalis. Note the shape and actino-body round the
                                    horn behind the spine.

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2. Ovum of S. nasalis in uterus. Note shape. × 60. Photograph of
                                        fresh material.

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3. Ova of S. spindalis in uterus. Note shape. × 60. Photograph of
                                        fresh material.

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4. Section of liver of experimentally infected snail showing cercariae
                                        in sporocysts.