When her home was done, it was half as large as a big acorn and a charming place for Water Spider babies. The side walls and the rounding ceiling were all of the finest Spider silk, and the bottom was just one round doorway. The house was built under the water and fastened down by tiny ropes of Spider silk which were tied to the stems of pond plants. Mrs. Water Spider looked at it with a happy smile. "Next I must fill it with air," said she, "and then it will be ready. I am out of breath now."