28 PRINCIPLES OF EMBRYOLOGY 



field. Again, if a part of a field, either central or peripheral, is removed, 

 the remainder may compensate for the defect and become complete again, 

 while the isolated part can often become modified into a small but com- 

 plete field. 



SUGGESTED READING 



The main reference books are : for descriptive embryology of invertebrates, Heider 

 (1936); of vertebrates, Nelscn (1953); for experimental work, Schleip (1929), Lehmann 

 (1945, ecbinodernis and Amphibia only); for biochemical aspects, Needham (193 1, 

 1942), Brachet (1944). Two of the most important foreruimers of modem embryology 

 were Driesch (see 1929) and Roux (whose views are discussed in Needham 1936a and 

 Russell 1930). 



There have been several general conferences and coUoquia on embryology in recent 

 years; those published by the Society for Experimental Biology ('Growth', Second 

 Symposium, 1948), the New York Academy of Science {Annals, Volume 49) and in 

 the Revue Suisse de Zoologie, Volume 57 (Supplement), are particularly worth reading. 



For the relations between embryology and phylogeny, de Beer (195 1). 



