However, the Würtzburg school was at least agreed as to _method_, which was the main thing; its leaders were determined to press on to the solution of these problems on purely scientific lines. Everything was to be brought into a logical relation of cause and effect, and there was to be no intrusion of the supernatural, no mysticism. Natural laws must be traced in the life of the cells and in the history of the ovum and the embryo. The cells were to be regarded in the same way as the astronomer regards his myriads of glittering bodies. In this way the science of histology had been founded, and embryology had assumed a scientific character in the hands of Von Baer. The microscope kept the attention of students to facts, and did not suffer them to lose themselves in the clouds. Thus a foundation-stone was laid in Haeckel’s thoughts which he would never discard. In the later years of the Darwinian controversy he was destined to come into sharp conflict with both Virchow and Kölliker. Each of them came to look on him as the sober hen does on the naughty chick it has brought into the world, that madly tries to swim on the treacherous waters of Darwinism. But forty years afterwards—after many a knife-edged word had been thrown in the struggle—the aged Kölliker was one of those who entered their names in the list of men of science who erected a bust in the Zoological Institute at Jena in honour of Haeckel’s sixtieth birthday. However, it was a different, an apparently trivial, yet, as it turned out, most momentous interest that quickened him during these University years.