10 



statements seen in print support the theory that abnormalism 

 is due to over-production — the female being forced to lay an un- 

 usually large number of eggs by being frustrated in her first at- 

 tempt to incubate. Now I find this apparently true in some in- 

 stances, but the rule cannot be applied to all, nor even, with any 

 degree of certainty, to the majority of cases. It also seems rea- 

 sonable, at first thought, to believe that over-production would 

 invariably bring about this result, but I am inclined to view it 

 in a different light. It prob ibly depends upou our interpreta- 

 tion of the term over-production; if "excessive laying" expresses 

 it, then the second Bet of eggs of a rtain species which habitual- 

 ly rears but one brood annually may be considered an over-pro- 

 duction; but those birds which annually rear more than a single 

 brood must be accorded a larger normal laying. 



There are several instances on record where the common 

 Flicker (Colaptes auratua)', has been subjected to long continu- 

 ous laying With various normal and abnormal results, which go 

 to show that some individuals are able to withstand this exces- 

 sive laying, while others of the same species, thus subjected, ter- 

 minate abnormally. 



With a view of ascertaining what effect the continuous lay- 

 ing would have on the Bluebird (Sialis sialia) I erected a box for 

 a pair of these birds that came to our premises early in the 

 spring of 1886. They immediately took possession, built a nest 

 and deposited five eggs which I took, as I did also three of the 

 four subsequent sets laid; the last set I left for the birds to hatch. 

 These eggs — twenty-one in number— were all normal and of uni- 

 form size, shape and color. The laying of these five sets and the 

 time intervening occupied about thirty-five days. 



Another case of the continuous laying of the Bluebird, but 

 which resulted differently, is described in "Descriptions of Sets" 

 number 22; in this the color abruptly changed from normally 

 pale blue in the first to pure ivhite in the second clutch. 



Whatever the ultimate rssulis of over-production may be I 

 am prepared to assert from personal observations that many ab- 

 normalities are brought about by causes far removed from that 

 of over-production. These examples are found among sets of 

 the first laying, which, as a matter of fact, cannot be attributed 

 to over production. Of the one hundred and ten sets treated 

 in this paper, thirty-nine are known to be first layings and 

 twenty-three others are believed to be firsts but no positive 

 evidence of the fact has been established. 



The following groups have been arranged, showing the or- 

 der in which the sets were laid; the grouping and numbering 

 are arranged to conform with that of "Descriptions of Sets." 



