PRINCIPAL AXIS OF SYMMETRY IN THE BIRD S EGG. 331 



below). Haller made mention of this in 1758 and Fere (1897) 

 has called particular attention to it. 



G. The Oviducal Orientation. How does the egg lie in the 

 oviduct? What is the relation of the principal egg axis with its 

 differentiations to the axis of the oviduct? This has always 

 been a matter of interest and it has been very naturally associated 

 with the question as to which end of the egg is laid first. Aris- 

 totle says the blunt end is laid first and his whole argument con- 

 cerning the "principium ovi" seems to assume that this end 

 passes first down the oviduct. Purkinje published the data for 

 the understanding of this matter in 1825 (see especially pages 21 

 and 22 of the 1830 edition) and he was fully confirmed by von 

 Baer (1828-1837) anQl Coste (1847), but this was all forgotten 

 and the question was discussed in the seventies and eighties 

 to little purpose. It was finally put to rest by Wickmann in 1895. 



It should be said first that all observers who have made 

 extensive studies of oviducal stages in birds agree that the pointed 

 end passes first down the oviduct. For the hen the following 

 may be cited: Purkinje (1825), von Baer (1828), Coste (1847, 

 p. 293), Kiitter (1878), Taschenberg (1885), Wickmann (1895) 

 and Patterson (1910). In the pigeon the pointed end when 

 recognizable was always found to be cloacal by Blount (1909) 

 and Patterson (1909), each of whom studied about 150 oviducal 

 eggs, and this has been my own experience. The same condi- 

 tions have been reported for a hawk by Kiitter (1878), the canary 

 and various other birds by Wickmann (1895). It may be said 

 in passing that Meckel von Hemsbach announced in 1851 that 

 it was a mathematical necessity for the blunt end to pass first 

 down the oviduct! J. A. Ryder (1893) has also worked out the 

 mechanics of shell formation on this basis. 



There are however numerous observations which leave no 

 doubt but that the blunt end of the hen's egg is usually laid 

 first as Aristotle said. Nathusius gathered data in 1885 and 

 obtained only a single authentic record of the pointed end having 

 been laid first. Landois (1877), Konig-Warthausen (1885), Jasse 

 (1886) and Erdmann (1886) all gave evidence from direct 

 observations or from the direction in which the blood streaks of 

 pullet's eggs were rubbed, that the blunt end is laid first. Nathus- 

 ius (1885) reported a series of observations by Frau A. Ernst 



