338 GEORGE W. BARTELMEZ. 



spends exactly to what I found to be the greatest variation in the 

 eggs of an individual pigeon (see p. 347). His results may be 

 summarized as follows: 



Total control eggs with normal embryos i,337 



Total experimental eggs with normal embryos 1,588 



Percentage of normal eggs with deviation of more than 45 21.39 per cent. 



Percentage of experimental eggs with deviation of more than 45 . .28.82 per cent. 



In 1908 Rabaud published an exceedingly interesting study upon 

 variation of axis angles in the hen's egg. He determined first 

 from a series of 105 eggs taken at random that as much variation 

 might be met with normally as was reported by Fere, Blanc, and 

 Ferret et Weber in their experimental series. This is shown in 

 the following tabulation of his results: 



o 3 



10-40 2 



45 20 



50- 70 18 



90 9 



110-130 15 



135-. - J 4 



140-170 5 



180 o 



270 (inverted) 12 



Rabaud showed also by a series of observations on over 100 eggs 

 with windows in the shell that in the course of the first five or 

 six days' incubation the axis angle does not change. 



For the pigeon Patterson (1909) gives the usual axis angle as 

 45 (see my 1912 paper, p. 300), whereas Blount (1909) mentions 

 variations such as 60 and 150, but regards these as "compara- 

 tively rare." My own results which showed much greater varia- 

 bility for the pigeon's eggs and indicated less variability for the 

 eggs of a given bird are discussed on page 347 below. 



The only other reports on the relation of embryo to egg in 

 birds are those of Haswell (1887) for the emu and Fere (1896) 

 for the duck. The former found all the relations described by 

 v. Baer for the hen's egg. The embryo was "usually at right 

 angles" but "not infrequently oblique though never longi- 

 tudinal" to the principal egg axis. Fere (1896) compared the 

 axis angles in the duck with the hen and found they agreed 

 except that the duck showed greater variability. In a series of 

 74 eggs of each kind, 75 per cent, of the duck eggs showed a 



