PREFACE 



In IIk' preparation of Section 11, Parts II and 

 III, it lias been necessary to deviate from the 

 arrangement proposed in the original annomice- 

 ment. J)iiring the course of preparation it be- 

 came evident that the treatment of the subject, 

 as developed by the various authors, would re- 

 sult in more pages than can be saddle stitched 

 into one cover. It also became evident that it 

 ^ would be impossible to complete some of the 



chapters dealing with free-living and plant- 

 parasitic nematodes until long after most of 

 the others were ready for printing. Hence it 

 g r^ seemed advisable to so change the^rrangement 



of the chapters as to permit the inunediate pub- 

 lication of completed manuscripts even though 

 it was necessary to modify what might seem the 

 most logical sequence. 



The various authors are responsible for the 

 facts presented and the opinions expressed in 

 the parts accredited to them with the one ex- 

 ception of taxonomic nomenclature, for which 

 Dr. B. G. C'hitwood assumes responsibility. 



To the contributors I wish to express my ap- 

 preciation and thanks for their sympathetic co- 

 operation as well as for the excellence of their 

 contributions and the care and thoroughness 

 with wliich these were prepared. 



J. R. Christie. 



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