'While the young [fish] are small and not yet fully developed they have veins of great length which take the place of the navel-string, but as they grow and develop, these shorten and contract into the body towards the heart, as we have said about birds. The young fish and the eggs are enclosed and in a covering, as are the eggs and young of birds. This covering resembles the dura mater [of the brain], and beneath it is another [corresponding therefore to the pia mater of the brain] which contains the young animal and nothing else.'[50] [50] The enormous _De Animalibus_ of Albert of Cologne is now available in an edition by H. Stadler, _Albertus Magnus De Animalibus Libri XXVI nach der cölner Urschrift_, 2 vols., Münster i/W., 1916-21. The quotation is translated from vol. i, pp. 465-6. In the next century Conrad von Megenberg (1309-98) produced his _Book of Nature_, a complete work on natural history, the first of the kind in the vernacular, founded on Latin versions, now rendered direct from the Greek, of the Aristotelian and Galenic biological works. It is well ordered and opens with a systematic account of the structure and physiology of man as a type of the animal creation, which is then systematically described and followed by an account of plants. Conrad, though guided by Aristotle, uses his own eyes and ears, and with him and Albert the era of direct observation has begun.[51] [51] Conrad's work is conveniently edited by H. Schultz, _Das Buch der Natur von Conrad von Megenberg, die erste Naturgeschichte in deutscher Sprache, in Neu-Hochdeutsche Sprache bearbeitet_, Greifswald, 1897. Conrad's work is based on that of Thomas of Cantimpré (1201-70).