December 16, 1910] 



SCIENCE 



873 



Bf . bf Xiif bF^Bf . Bf = Barred <?£?, 

 + bf .Bf = Barred t?(^, 

 + Bf . 6F = Barred 5?, 

 + 6f . 6F =: Non-barred $?. 



The expectation here is that all the c? prog- 

 eny will be barred and of the ? progeny one 

 half will be barred and one haK non-barred. 



Experimental Result. — There were 9 ma- 

 tings of this kind made. From these ma- 

 tings were produced 69 c? chickens — all barred 

 — and 66 S chickens, of which 29 were barred 

 and 37 non-barred. 



VIII. Mating: F^ Cross-bred ^ X 'Non-harred F^ 



Cross-bred $. 

 Expectation : 



Bf .bfxbf .bF = Bf .bf = Barred ^J, 



■^ bf . bf = Non-barred (J<5', 



+ Bf . 6i? = Barred ??, 



+ bf .bF = Non-barred 5$. 



The expectation here is that barred and non- 

 barred birds will appear in equal numbers in 

 both c? and ? progeny. 



Experimental Result. — There were 8 ma- 

 tings of this kind made. From these matings 

 were produced 58 d" chickens, of which 27 were 

 barred and 31 were non-barred, and 39 S 

 chickens, of which 13 were barred and 26 were 

 non-barred. 



This completes the total number of possible 

 matings. The experiments include all told 

 670 adult recorded F„_ chickens. 



Discussion of Results. — From the results 

 above set forth it is apparent that as regards 

 the appearance of the different types of hirds 

 in the different matings, theory and fact are 

 in close accord in all cases. More precise and 

 clear-cut results than have been obtained in 

 this experiment would be difficult to find. The 

 precision and definiteness of the results is 

 emphasized by the fact that in every case an 

 ohjective description of the hird was made and 

 recorded without any hnoivledge on the part 

 of the describer of its pedigree or the char- 

 acters which it would theoretically lie ex- 

 pected to hear. No attempt was made even to 

 work out in the laboratory the theoretical F, 

 expectations until after all the data (descrip- 

 tion of birds) were collected. In fact these 

 F, expectations which appear above were 

 never set down on paper by any one in this 



laboratory until late this present fall, after 

 all the experimental results were collected and 

 tabled. The objectivity of the work could 

 not have been more thoroughly safeguarded. 

 All the original descriptions of the birds were 

 made by the same person, E. P. 



There is one point in regard to which it 

 might at first be thought that there was seri- 

 ous disagreement between theory and fact. It 

 will be noted that in matings V., VI., VU. 

 and VIII., there is in each case a more or less 

 marked discrepancy between the expected and 

 the actual numbers of barred female progeny. 

 In matings V. and VII. the discrepancies are 

 small, and may easily be explained as purely 

 chance deviations. In the cases of more seri- 

 ous discrepancy, as well as in these two, the 

 number of barred females actually found is 

 in each case smaller than the expected num- 

 ber. The explanation of this is probably not 

 that we have here an exception to Mendelian 

 expectation. On the contrary we have every 

 reason to believe that the explanation is much 

 simpler and consists mainly in the fact that 

 barred females were systematically stolen 

 from the plant during the summer. As has 

 been said it is necessary in working with the 

 barred pattern to wait until the birds are in 

 adult plumage before they can be recorded. 

 Now it happens that, fortunately or unfor- 

 tunately, the Maine Stations Barred Rock 

 stock is locally held in high esteem for its eco- 

 nomic qualities. The location of the houses 

 upon the range this year, and other circum- 

 stances as well, made it impossible to control 

 thieving, and a large number of birds were 

 lost in this way. The majority of the barred 

 F. cross-bred females were indistinguishable 

 from pure Barred Rock females to a casual ob- 

 server. Many of them were undoubtedly 

 stolen on the supposition that they were pure 

 Rocks. A careful and thorough study of the 

 evidence has left no doubt in our minds that 

 the above is an important factor in the ex- 

 planation of the discrepant ratios. Every ex- 

 perimentalist will appreciate our feelings when 

 the discovery of these depredations was made. 

 The whole case illustrates very well the con- 

 dition which one working in a state agricul- 

 tural institution is liable at any time to be 



