Thomas Morgan was an embryologist - Thomas Hunt Morgan - who had worked at the turn of the century in many subjects and had discovered that he'd come to the end of what he could do with classical embryological techniques. And this is why in the beginning of the century he turned to genetics, because he thought that in genetics he would learn something, have a different approach to developmental biology, which he just felt had, had reached, a dead end. And of course he established drosophila as a experimental organism, and drosophila had this 50 years... growth and development and one felt, well, now one's come to the end of the genetic deviation and one must go back to the problems of biology that had been left behind, namely those of development.