22 PROCEEDINGS OF THE 



published each year in Cassinia, showing the date of first arrival 

 for all the species on our schedule at the stations within the Phila- 

 delphia ten-mile radius and for a part of the species at localities 

 farther distant. Study, however, has shown that variation within 

 an area of say twenty miles is more a matter of time devoted to 

 observation and of local conditions than actual progress of migra- 

 tion, and the "first arrival" may just as well be recorded from the 

 most northern station in such an area as from the most southern. 

 The date of "general arrival" in our district, as computed for 

 many years past, is the really important date resulting from the 

 Club's records, and from it comparisons may be made between 

 different years or between this and other regions when similar 

 dates of "general arrival" are computed. 



The dates for the numerous individual localities, while abso- 

 lutely essential for computing the date of "general arrival," are 

 not in themselves of sufiicient importance to warrant the expense 

 involved in their publication. 



In view of these facts we propose in the future to publish, in 

 »ne table, the earliest arrival of each species at any station within 

 the Philadelphia ten-mile radius, and the date of "general ar- 

 rival" for this area; with the addition of all notes on rare species 

 or unusual occurrences as submitted by the entire migration corps. 

 The original return schedules will be kept on file at the Acad- 

 emy of Natural Sciences and are available for study so that spe- 

 cial reports may be compiled from them in the future. 



We trust that our observers will continue their observations, 

 and make returns as heretofore, and enlist others in the work 

 so that the D. V. O. C. migration record will continue to hold 

 its enviable position. 



