14 



Scientific Proceedings (117). 



The sex of the twins from the large twin-yielding ova (sex 

 known for first 3 cases only) is of real importance; for, much 

 earlier work by the author has shown that in pigeons the females 

 arise from larger ova and males from smaller ova. Each of the 

 three present cases supplies a rigorous test of the validity of that 

 conclusion, — and each affords a confirmation. If either of these 

 extraordinarily large ova had produced male twins, it would have 

 directly contradicted the conclusions drawn from related lines of 

 study conducted over a period of several years. If prospectively 

 male twins were present in this series they were necessarily con- 

 fined to origins from yolks of relatively small size. 



TABLE L 



Size of Eggs Yielding Twins Compared with Other Eggs from Same Bird. 



No. of 

 Female 

 Parent. 



Clutch. 



1 



Date. 



Data c 

 win-be; 



W't. 



>n Eggs 

 iring Clu 



Per 

 Cent, of 

 Diff. 



at 



tch. 



Sex (or 

 Stage). 



Average 

 Weight of 

 5 Eggs 

 Laid by- 

 Same Female 

 Immediately: 



Maximum and 

 Minimum Weights 

 for Other Than 

 Twin-bearing 



Eggs 

 (Same Year). 



Be- 

 fore. 1 



Af- 

 ter. 1 



Maxi- 

 mum. 



Mini- 

 mum. 



Total 



A248. . . 



Ki 



4/7 



7-43 





c? 



7.62 



8.11 



8.22 



7.10 



23 





K2 



4/9 



10.63 



+43-1 



9 9 



8-75 



8.92 



9.17 



8.46 



22 



60. . . 



Fi 



3/5 



8.07 





0* 



8.21 



7-58 



8.68 



6.72 



22 





F2 



3/7 



10.08 



+24.9 



9 9 



8.13 



7.84 



8.65 



6.IS 



21 



V 4 9 2 ■ - 



Di 



10/16 



15-77* 





& 



14.80 



1705 



17.40 



14.80 



8 





D2 



10/18 



20.60 



+30.6 



9 9 



15-33 



18.06 



18.23 



15-33 



7 



P450. . 



Di 



5/30 



8.92 





& 



8.76 



9.02 



9.21 



7.82 



17 





D2 



6/1 



10.30 



+ 16.5 



(4-5d.) 



8.90 



9.-7 



9-75 



8.12 



14 



K465. . . 



Ei 



3/4 



8.00 





(i.od.) 



7-59 



7-95 



8.87 



6.87 



17 



K465... 



E2 



3/6 



8.05 



+ 0.6 



(2. 5 d.) 



8.24 



8.50 



9.29 



7.82 



13 



K 



5/14 



8.47 





(4-Sd.) 



7-95 



8.18 



8.87 



6.87 



17 



P843.. 













8.50 



8.64 



9.29 



7.82 



13 



Ci 



3/i5 



6.40 



- 3-7 



(3-od.) 



7-5i 



7.04 



(?) 



(?) 



2 





C2 



3/i7 



6.64 





(2.0d.) 



7.10 



6.90 



(?) 



(?) 



3 



1 In some instances the twin-bearing clutch was preceded or followed by fewer 

 than 5 eggs (see second and last columns). 



'Common pigeon; all other groups are ring-doves. 



Note. — The weights of twin-bearing eggs are set in italic type. First and second 

 eggs of the clutch are kept separate throughout the table. 



