He did not then realise the full bearing of this observation, which really constituted the basis of his future phagocyte theory; this was only to appear eighteen years later. He had also made researches on numerous specimens of insects and on the scorpion, establishing the fact that they all had embryonic layers; he concluded that he was "entitled to extend the theory of embryonic layers to Arthropoda." Finally, he had discovered embryonic layers similar to those of the Vertebrates in inferior Invertebrates, the Cephalopoda (Sepiola). This established a link of continuity between the higher and lower animals. CHAPTER XII Petersburg--Baer prize--Return home--Friendship with Cienkovsky --Odessa--Naturalists' Congress at Petersburg--Departure from Odessa--Zoological Lecturer's Chair at Petersburg--Messina--Enforced rest--Reggio--Naples--Controversy with Kovalevsky--Visit to the B. family--Mlle. Fédorovitch--Educational questions--Difficulties of life in Petersburg. During his stay abroad, Metchnikoff had successfully carried out several researches, and this allowed him to apply for a post of _docent_ at the new University of Odessa, which he had chosen on account of its proximity with the sea and its marine fauna. Whilst awaiting the result he went to Petersburg in order to pass his thesis and to prepare himself to become a professor. He received a pleasant welcome, for his lively and sociable disposition had made him many friends. The brothers Kovalevsky, with whom he was already on friendly terms, offered him hospitality; he also made the acquaintance of Professor Békétoff, and soon became a member of his family circle. He was well received everywhere, for his scientific precocity excited general interest. He was even elected _magister_[10] by the Faculty, without having to pass an examination, on account of the work he had done. He and Kovalevsky halved Baer's first prize, and they were invited and treated with the utmost kindness by Baer himself. Metchnikoff had certainly entered upon a successful phase; his friends nicknamed him "the star." As soon as he was made a _magister_, he received his appointment at the Odessa University, and, the holidays drawing near, he was at last able to return to his home. Needless to say how joyfully and lovingly he was received by his family. He spent two months with them, utilising his leisure in preparing himself to teach. [10] A degree preceding that of Doc.Sc.