TON BAER AND RISE OF EMBRYOLOGY. 



109 



J r sM«ss<. 



3pc 



p 



«*'««riKr,57^. ~- 





! 4\ r 





# 



Fig. 6. Plate from Wolf's Theoria Gmerationis (1759), showing Stages in 

 the Development of the Chick. 



which must have been condensed in the ovary of Eve, arrived at the 

 amazing result of two hundred millions. 



Work of Wolff. — Wolff, as a young man of 26 years, set himself 

 against this grotesque doctrine of preformation and encasement, in 

 his ' Theoria Generationis,' published in 1759. This consists of three 

 parts : One devoted to the development of plants, one to the develop- 

 ment of animals and one to theoretical considerations. He contended 

 that the organs of animals make their appearance gradually, and 

 that he could actually follow their successive stages of formation. 



The figures in it illustrating the develoment of the chick, some of 

 which are shown in Fig. 6, are not, on the whole, so good as Malpighi's. 

 Wolff gives in all seventeen figures, while Malpighi published eighty- 



