1867.] 



President's Address, 



175 



sufficient to demonstrate, even without special scientifiG investigation, that 

 their young arose within eggs, and that these eggs were preformed within the 

 body of the virgin female. Further, the researches of Fabricius, of Harvey, of 

 Haller, of Caspar Friedrich WolfP, of Cruikshank, of Dollinger, of Pander, 

 of Prevost and Dumas, and of Dutrochet and Cuvier had traced back the em- 

 bryos of the Ovipara to a very early stage, and had thrown much light upon 

 the changes undergone by those of the Mammalia. But the earliest condition 

 of the mammalian em.bryo was unknown. Haller's authority was still pre- 

 dominant ; and Haller's researches had enabled him to discover in the mam- 

 malian uterus, shortly after im.pregnation, nothing more than a semifluid 

 substance, in which, it was imagined, the embryo appeared by a kind of 

 crystallization. The origin of this semifluid embryonic matter was sought 

 for in a mixture of the seminal fluid of the male with the contents of the 

 remarkable vesicles long before discovered by De Graaf in the ovary of the 

 female, and called after him the Graafian folHcles. 



But in 1827 all such speculations were at once abolished, and the identity 

 in mode of origin between the embryos of the Mammalia and those of other 

 animals was demonstrated by a young Professor in the University of Konigs- 

 berg, whose unwearied patience, sagacity, and sharpsightedness had enabled 

 him to trace back the foetus, step by step, to the minute egg, not a hun- 

 dredth of an inch in diameter, to demonstrate that the Graafian follicle is 

 simply the chamber in which that egg is contained, and to prove that the 

 first step in mammalian generation, as in that of other animals, is the de- 

 tachment of the egg from the organ of the parent in which it is developed. 



This capital discovery forms one of the grounds upon which the Copley 

 Medal is to-day awarded to the sometime Professor in Konigsberg, but now, 

 and for many years past, the honoured iVcademician of St. Petersburg, Karl 

 Ernst von Baer. 



Von Baer's great discovery was not the result of accident, but was the 

 reward of long-continued and most laborious investigations into the deve- 

 lopment, not only of the chick and of the mammalian embryo, but of other 

 animals. The first part of a great work entitled " Ueber Entwickelungs- 

 geschichte der Thiere. Beobachtungen und Reflexionen," embodying some 

 of the results of these inquiries, and mainly of the investigations into the 

 development of the chick, appeared in 1828; the second part, in which 

 the mammalia are chiefly treated of, was published in 1837. 



It is impossible to overestimate the value of this remarkable book, or to 

 doubt the great influence which it has exerted, and still exerts, upon the 

 growth of a sound philosophy of Biology. 



At the time of its appearance there was nothing that could be compared 

 v/Ith it, as a special monograph upon the formation of the chick, or as a 

 treasury of accurately observed facts respecting the development of the 

 Vertehrata in general, or as an exposition of the significance of development 

 and of the bearing of the study of embrj'^ology upon classification. And, 

 as a whole, it may be safely said that it remains at the present day, though 



