In his Memoir he gives an account of his meeting with D'Arcy Thompson.
The academic community at St Andrews was small, but very friendly and sociable. Although I was but an insignificant post-graduate student I soon got to know most members of the teaching staff, including the Heads of other Departments. With one of these my encounter had a mathematical aspect. Sir d'Arcy Thompson was the Professor of Zoology. He was a man of impressive appearance: a white beard, a strong voice and the bearing of a "real" professor, he was admired for the remarkable breadth and variety of his knowledge. He had a sonorous voice and was a fluent and powerful speaker. Trained at Trinity College Cambridge he remained attached to his alma mater throughout his life. Even as an old man he would make the journey from St Andrews to Cambridge in order to take part in a "Feast". On one of these occasions I asked him after his return to St Andrews if he had liked the excursion. He replied: "The company was delightful. But the meal was abysmal; when I was at Trinity, the College could boast of some of the finest kitchens in England. But now they buy their provisions at the Co-operative Stores. I would willingly spit upon their graves."
Apart from his own subject of biology, he was a highly competent classical scholar and he was fond of exercising his skills as an amateur of mathematics. His masterpiece On Growth and Form was a classic; in it he used quite sophisticated mathematical methods to elucidate the shapes that occur in the living world and bearing witness to his linguistic prowess the book is replete with long quotations in French, German, Latin and classical Greek (with no English translation). When I met him, he was engaged in writing a new and revised version of his book. One of the topics he was interested in required the use of differential equations, a subject which evidently lay outside d'Arcy Thompson's fields of knowledge at that time. So one day when he saw me in the University Library he said: "Do you know anything about differential equations?" When I replied that I was familiar with the usual facts in this subject, he put his arm on my shoulders and said: "Here is a good boy. Come along with me to my house and tell me all about it." So I went to his house with him, sat down at his desk and wrote out the answer to his question.