white herons (138) in Europe are much larger than eggs 

 laid by the same species in India, without, so far as the 

 writer can learn, any difference in the incubation periods, 

 of the European and the Indian birds. 



It is self-evident that size, when determined by linear 

 measurements, is an exceedingly shifting datum on which to 

 base comparisons of different incubation periods. If there 

 be any relation between these periods and the egg size or 

 bulk, it seems important to secure a better datum than the 

 above, and in a fresh egg's weight, the writer believes, one 

 has a datum beyond criticism, as to its meaning, and one 

 which is unaccompanied by any questionable secondary con- 

 siderations, and hence furnishes much more secure ground 

 on which to build comparisons, and from which to draw 

 conclusions. 



Unfortunately, the number of recorded egg weights 

 from different species, gathered by the writer for this study, 

 is very small, though there are, doubtless, many others 

 tucked away in inaccessible publications; the following list 

 (Table No. 4) gives all those found in literature, by the 

 writer, plus a few which were determined by him person- 

 ally. An additional list (Table No. 5), is given of the 

 weights of individual eggs occurring in sets. All weights 

 are in ounces and pounds (avoirdupois), and, so far as 

 known, are of fresh eggs, unless otherwise specified : 



TABLE NO. 4 /(H^"-M-^ IS. 



Weights of Bird Eggs in Ounces Avoirdupois 



Weight Authority 



Ostrich 48.00-60.00 10 



Ostrich avg. 60.00 141 



Emu 20.00 10 



Kiwi 14.00-20.00 10 



Kiwi 14.00-15.00 42 



Kiwi 14.00 168 



Emperor Penguin 16.00 20 



Adelie Penguin 4.80 136 



Adelie Penguin 4.56 20 



Yellow-headed Tropic Bird 1.42 26 



Loon (Sp?) avg. 4, 5.67 178 



Black-crown Night Heron avg. 4 sets, 1.25 178 



Mallard Duck (domesticated) avg. 2.83 78 



Pekin Duck (domesticated) 2.38-3.00 78 



Goose (toulouse) avg. 6.00 78 



California Vulture (estimated by W. H. B.) 10.90 10 



Sparrow Hawk 50 56 



Western Ked-tail Hawk 2.10 78 



Mallee Fowl (Lipoa ocellata) 6.50 186 



Globose Curassow ; 8.00 169 



Domestic Turkey avg. 3.23 78 



33 



