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TIlE CONDOR VOL. X possible to file these slips under the vertical system unless they were enclosed in something of uniform size. And last but not least the great ease with which any desired data may be found in a vertical system of this kind makes it the handiest system imaginable. Another idea which Mr. Dille has worked out is an "autograph data" blank, which is of the same design as his regular blanks, but which he sends to collectors who furnish him with sets and has them write the original data on ?is blanks but over their own signatures, thus giving him the original data on uniform blanks. A tabulated register of all sets coming into and leaving the collection, which A SERIES OF THE EGGS OF THE AMERICAN CROW SELECTED TO SHOW VARIATION gives the date, species, locality, collector, incubation, from whom secured and to whom disposed, is also a great assistance in a well ordered collection, altho many collectors seem to feel that this is superfluous. One might continue indefinitely to jot down the hundreds of little hints and ideas that are produced by continuous experimenting, but I have covered the points which have always given me the most trouble and I hope they may prove of benefit to the reader interested in this line. ])enz?er, Colorado.