Thus, many of the critical remarks appear in this volume only as 

 reflected in the minds of the authors to whom they were addressed. 



A few of the remarks contributed essentially new material or a 

 new point of view, and in these cases the speakers later prepared the 

 text to be included here. 



Four reports submitted for the conference are not included in the 

 present volume. Dr. Isabel Morgan Mountain had written a very in- 

 teresting report on immunity to mammalian viruses. It was felt how- 

 ever that the phenomena discussed by Dr. Mountain, being entirely 

 specific to mammalian hosts, fell too little within the scope of this book 

 whose chief purpose it is to compare the different virus groups. Dr. 

 C. W. Bennett had written a report on interference in plant viruses, 

 but preferred not to have his paper included, since he is now writing 

 a review article on this subject which is scheduled to appear in next 

 year's Annual Review of Microbiology, and will embody results of ex- 

 periments now in progress. Mr. Bawden's discussion remark on inter- 

 ference fills this gap in some measure. Drs. S. G. Wildman and R. D. 

 Owen discussed their current work on the relationships between host 

 protein and virus protein in tobacco mosaic disease, but wished to post- 

 pone publication of this study until certain crucial experiments now in 

 progress are completed. N. W. Pirie, although not able to attend the 

 meeting, very kindly contributed a paper entitled "The biochemical 

 approach to viruses." At the request of the editor, Messrs. Bawden 

 and Pirie substituted for this paper the one here included, which is 

 more explicit in presenting the data to which Mr. Pirie's arguments 

 referred. 



An explanation should be added about the sequence in which the 

 material was discussed and the sequence in which it is here presented. 

 One might almost say that if we knew a logical order of presentation 

 the conference need not have been held. It is just the uncertainty of 

 the homology and of the interpretation of many of the facts which 

 was the topic of discussion, and, needless to say, much of this uncer- 

 tainty still remained at the end of the conference. At the conference 

 we did make, nevertheless, a timid attempt at a logical sequence, work- 

 ing our way from the stage of adsorption of a virus, through the stage 

 at which interference may be presumed to occur, to the more intimate 

 stages of virus reproduction, where chemistry, immunology, and ge- 

 netics are trying to blaze their respective trails, not knowing whether 

 or where they will meet. We moved back and forth freely among the 

 three groups of viruses, permitting free rein to the demands of the 

 subject matter. 



In presenting the material in printed form we have chosen a 

 different sequence. Luria's paper is presented first since it is more 



