Oken's article was apparently one of the very few 

 responses to Pander's work, aside from K. M. Baer's. (74) 



Pander acquainted himself with Oken's review, and his 

 detailed answer soon appeared in I SIS. 33 Oken in turn was 

 interested in Pander's reply; hence in printing it he added 

 his own observations, which he put directly into the text. (75) 

 Expressing his delight for Oken's interest, Pander said that 

 he hurried to answer the questions posed in the review. 



Concerning "chalazae," Pander referred to the German 

 text of his work, in which the investigation is given in a 

 different way than in the Latin text, not in regard to the 

 periods of development but in regard to the organ system. 

 There the chalazae are explained as twisted growths of the 

 yolk membrane. The twisting of the chalazae is not a result 

 of frequent turning of the eggs, as Oken thought, because 

 the chalazae are twisted even in eggs that are just laid. 

 There is no cross canal in the chalazae; they do not 

 participate in the suction of the albumen and disappear 

 early, along with the yolk membrane. The albumen, in 

 general, is not used at the beginning of incubation as a 

 food material; its diminution simply depends upon the drying 

 which takes place in the fertilized as well as in the 

 unfertilized egg, as the following data shows. One fertilized 

 egg weighed 805 grains before incubation, and after the lapse 

 of twenty days it lost 131 grains; another unfertilized egg, 

 at the beginning, weighed 785 grains, and within the same 

 period in the incubator lost 121 grains. The loss in weight 

 is observed in eggs kept at room temperature. For two months 

 one of two investigated eggs lost 96.5 grains, and the other 

 lost 63.5 grains. To Oken's unsubstantiated suggestion about 

 the nature of the chalazae, which ascribes to them a. role in 

 feeding the embryo, Pander responded with a simple but 

 convincing experiment. 



Oken's next question concerned the formation of the 

 blastoderm, which Pander addressed by dismissing Oken's 

 error on the genetic connection of the blastoderm and the 

 yolk membrane. "The blastoderm," Pander wrote, "is an 

 entirely isolated part, existing already in the non-incubated 



33. Pander, "Entwickelung des Kuchels," ISIS, v. 3 

 (1818) , p. 512-524. 



264 



