Answer:
He is easy-going but disorganized
Step-by-step explanation:
"For more than thirty years the doctor had thrown into it every page he
wrote, from brief notes to the complete texts of his great works on heredity. "
30 years of papers in a bookshelf is disorganized.
"...when he at last found the one he was looking for, he smiled."
He smiled when he found his own paper in his own bookshelf - i say hes easy going.