If botany was the field of Ray's greatest and lifelong interest, it is by no means his only or even perhaps his chief claim to the gratitude of posterity. In it, as we have seen, he accomplished work which would of itself make a fine record: to it, as he constantly claims, he returned from other excursions as to his proper task. But the astonishing feature of his career is not his mastery of a single subject, but the range of his knowledge and the value of his parerga. In these days of specialisation it is difficult to believe that a man could make himself expert in the whole of zoology literally as a sideshow and in the intervals of his main study; and Ray himself never claimed to have done so. But the fact remains that after Willughby's death he set himself to produce books on birds, fishes, mammals and reptiles, and insects; and that these books, even more than his botanical writings, laid the foundation for serious scientific progress in each subject.

It has been customary to regard this aspect of his work as little more than the editing of his friend's material and to give Willughby the credit for the result.