MODERN BIOLOGY 363 



portion towards its solution. In the following we shall deal with Pander, 

 who investigated the germ layers in the embryo of the hen; Rathke, who dis- 

 covered the branchial slits in the embryo and the circulation in conjunction 

 therewith; and, in another connexion, Purkinje, who discovered the germ- 

 cell in the hen's egg. The first place among the creators of modern embryol- 

 ogy, however, is held by von Baer, one of the great personalities in the field 

 of research in the nineteenth century. 



Karl Ernst von Baer was born in 1791 on the Piep estate in Esthonia, 

 the son of a landowner belonging to the German nobility of that country. 

 Upon leaving school at Reval he matriculated at the recently founded Uni- 

 versity of Dorpat, where he applied himself to medicine. He continued his 

 studies in branches of that subject in Vienna, but from there, realizing that 

 he was not made for a doctor, he proceeded to Wurzburg in order to be trained 

 as a theoretical scientist. The teacher of anatomy in that university at the 

 time was Ignaz Dollinger (1770-1841), a disciple of Schelling's, who, 

 combining his master's passion for philosophical speculation with a radical 

 knowledge of anatomy, especially interested himself and his pupils in prob- 

 lems of evolutional history. It was here that von Baer's research took the 

 course in which he was eventually to go further than any of his contempo- 

 raries. After completing his studies he was appointed professor at Konigs- 

 berg and carried out his principal investigations at that place. In 1834 he 

 accepted an invitation to become an academician at St. Petersburg. There his 

 activities won a brilliant success, and honours were lavished upon him ac- 

 cordingly. The scientific works of his old age, however, do not possess the 

 same importance as those of his early years. This is due primarily to the fact 

 that he to a great extent divided his interests; upon official request he under- 

 took several journeys to diff'erent parts of the Russian Empire and as a result 

 became interested in a number of different problems — anthropology, ethnog- 

 raphy, archasology, and even etymology. Having been allowed to resign his 

 post, he settled at Dorpat and died there in 1876. He was honoured by his 

 countrymen in many ways; the Esthonian nobility published at their own ex- 

 pense a splendid edition de luxe of the autobiography that he had written in 

 his old age, and after his death a bronze statue was raised to him at Dorpat. 



Von Baer discovers the egg of mammals 

 There can be no doubt that von Baer won his greatest fame through the 

 embryological works written in his youth. He published the results of these 

 in a brochure entitled De ovi mammalium genesi, which came out in 18x7, and 

 a larger work, IJber Entivicklungsgeschicbte der Tiere, of the years 1818 and 1837. 

 In the first-mentioned treatise he describes the most important of the dis- 

 coveries he made in this field — namely, the egg of mammals in the ovary. 

 Apart from the vague ideas of earlier scientists on this subject, de Graaf 

 (Part II, p. lyz) was the first to explain at all the conditions obtaining at the 



