summer of 1888, twenty-three years ago, at various phases of the journey, it was all a lonely pilgrimage
“Towards the unknown region,
Where neither ground is for the feet,
Nor any path to follow.”
New problems, entailing fresh, patient labours, constantly arose, and the solutions of these brought, invariably, new surprises in their train. The start of the work was the discovery of a transient nervous apparatus in the development of a fish ; this was the one end of the slender thread. Its unravelling was always intensely interesting and absorbing to the observer, and the thread went on, and on, and on, always continuously, unlike any other thread of research known to me in the whole history of embryology. Then, at last, the other end came in sight, twenty-five years after the observer first began, in Semper’s old research institute in the ancient University of \Würzburg, to learn from the master how research problems were to be approached, dealt with, and solved. The story of this is told in Chapter VI.
The first piece of work upon the thread occupied some five or six years: for that time was required to work out, night after night, and put together the results, which are recorded, with eight plates, in the memoir upon “The History of a Transient Nervous Apparatus” (1896). This was clearly an asexual structure, the work upon it a prelude to the cancer investigations. There are, indeed, published researches extant, such as Professor A. Goette’s immense monograph upon the development of a toad, Bombinator, which took a longer time; but, so far as I know the literature of embryology, there is no other embryological monograph which covers so long a period of development, or span of time, some seventeen