CHAPTER 25 



INVESTIGATIONS ON INVERTEBRATE EMBRYOLOGY: 

 WORK OF A. GRUBE, A. D. NORDMANN, 

 N. A. WARNEK, AND A. KROHN 



During the first twenty to thirty years of the nineteenth 

 century, embryology remained chiefly the study of the embryonic 

 development of vertebrates; the comparative peculiarities 

 of development of different animals was studied only at the 

 limits of this most studied group. By the end of the twentieth 

 year of that century, i.e. the period of Baer's active work 

 in embryology, the first investigations into the development 

 of invertebrates appeared. Baer himself, as mentioned above, 1 

 turned his attention to the characteristic peculiarities of 

 development of arthropods, noting in particular that their 

 blastoderms are situated on the abdominal side of the egg and 

 distributed from here in the dorsal direction. Baer was not 

 able to explain the development of arthropods more clearly. 

 Even the investigations of his predecessor Herold, which were 

 limited to the study of the late stages of development of 

 butterflies and spiders, 2 could not give Baer material for 

 well-grounded comparative embryological conclusions. 



The aspiration to apply embryological principles to 

 arthropod development was actualized by Baer, first in the 

 study of embryonic layers, reflected in the works of 



1. See Chapter 15. 



2. J. m. D. Herold, ENTWICKELUNGSGESCHICHTE DER SCHMET- 

 TERLINGE ANATOMISCH UND PHYSIOLOGISCH BEARBEITET 



(Cassel u. Marburg, 1815), vi + 118 + xxxiv pp.; EXERCITA- 

 TIONES DE ANIMALIUM VERTEBRIS CARENTIUM IN 0V0 

 FORMATIONE. DE GENERATIONE ARANEORUM IN 0V0 



(Marburg, 1824) , x + 63 pp. 



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