ii 



zoological museum . In the same year be was made Professor Extra- 

 ordinarius, and, looking upon himself as now settled at Konigsberg, 

 married Praulein von Medem. In 1822 he became Professor Ordi- 

 narius, and in 1826 succeeded Burdach as Professor of Anatomy and 

 Director of the Anatomical Institute. 



Ever since his arrival at Konigsberg he had devoted himself with 

 great energy to zootomy, and published several zoological and ana- 

 tomical papers, notable among which is one containing the first 

 exposition of his views on animal types. In 1818, however, he received 

 from his friend Pander a copy of the monograph on the development 

 of the chick, the study of which led him in the spring of 1819 to 

 commence those embryological investigations with which his name will 

 ever be connected. These were carried on with unwearied diligence 

 for seven years, and it was not until 1827 that he made his results 

 known in the form of a contribution to Burdach's Physiology. In 

 his capacity as editor, however, Burdach saw fit to make so many 

 changes and omissions as greatly to dissatisfy Baer, who determined 

 to publish his researches in an independent form. This he did in 1828 

 under the title of " Ueber Entwickelungsgeschichte der Thiere, Beo- 

 bachtung und Reflexion." Meanwhile, in the spring of 1827, he had 

 made the important discovery of the existence of the mammalian ovary 

 in the ovum. 



The " Entwickelungsgeschichte " consists, in the first place, of a de- 

 tailed chronological description of the development of the chick in the 

 egg ; and, in the second place, of general deductions and reflexions in 

 the form of scholia and corollaries. Almost immediately afterwards 

 Baer began a more general and systematic account of development 

 under the title of " Yorlesungen iiber Zeugung und Entwicklung der 

 organischen Korper." The first sheets of this were printed in 1829, 

 but the work was then interrupted for several years, and was finally pub- 

 lished without the author's permission in 1834 as the second part of 

 the " Entwickelungsgeschichte." 



In 1827 Baer received an invitation to become a member of the 

 Academy of Sciences at St. Petersburgh. This he did not immediately 

 accept ; bat in 1829, without resigning his professorship at Konigsberg, 

 made a journey to St. Petersburgh to see whether it would be possible 

 for him to carry on his investigations in that city. He found, how- 

 ever, the hindrances to work so many and great, that he declined the 

 call and returned to his old post, throwing himself with renewed 

 vigour into his studies. A few years later these incessant labours 

 began to tell upon his health. He grew enfeebled, his nights became 

 sleepless, and he began to fear that his work was ended. Just at this 

 juncture his elder brother, who was in possession of the family estate, 

 died, and his sisters strongly pressed him to undertake the charge of 

 the property which would eventually pass to his own son. These 



