may be some imperfections in citations. Nonetheless, with 

 the exception of some of the Russian articles, I have been 

 able to verify dates, page numbers, and other significant 

 reference data. Readers with access to a superior library 

 should be able to locate most of the material Blyakher cites, 

 though some of the unpublished Russian materials may well 

 prove inaccessible as they did to me. 



My other task in editing this volume lay in making the 

 descriptive chapters on von Baer's UBER ENTWICKELUNGS- 

 GESCHICHTE useful, since Blyakher 's page number refer- 

 ences to the Russian translation of von Baer's work would 

 obviously not be particularly relevant for most readers of 

 this English translation. Therefore, for the passages 

 Blyakher quotes or cites, I identified page numbers of 

 the German original edition, which has been reprinted 

 recently. And where necessary I checked, corrected, and 

 added the section references to UBER ENTWICKELUNGS- 

 GESCHICHTE. The references are thus: (volume, section, 

 German page number) or (volume, section, Russian page number 

 (German page number)). In addition, I corrected translation 

 of the quotations where necessary to accord with more common 

 English versions . 



For other references to or quotations from German or 

 English works, I made necessary corrections and substituted 

 standard English versions where available since some passages 

 had been distorted in the double translation. 



At this point, the first round of editing was complete. 

 Here Rosemary Regan enters the story. Ms. Regan, a marvel- 

 ously competent and intelligent assistant to Dr. Multhauf, 

 helped with typing some of the longer and messier chapters; 

 she corrected errors in the entire draft, and she used her 

 knowledge of editing and the history of science to polish 

 details of style and terminology. I thank Rosemary for her 

 considerable help and both Rosemary and Robert Multhauf for 

 their continued encouragement and good humor. 



With these acknowledgements and with the above caveats, 

 I feel assured that this descriptive volume should be accu- 

 rate and usable. Editing this has proven to be an unusual 

 project, as Dr. Multhauf warned, but I feel, as he has felt, 



