1893.] 



205 



[Ryder. 



girdle round the egg will tlie form of the Litter depart more and more 

 widely from the figure of a true ellipse and become more and moreovoidaj 

 or egg-shaped. 



The problem of the development of the figure of the hen's egg is one 

 that may be very easily dealt with mathematically. In fact, judging from 

 the great variety of variations of form presented by eggs it is probable that 

 a different equation would be required for every case, thus showing that 

 the forces operative in the process were themselves variable, a result 

 which is a priori most probable. The pressure preventing the passage of 

 the elliptical mass down through an elastic tube must be developed 



largely in the form of friction, and the resistance of the walls of the ovi- 

 duct to dilation. To overcome this a greater pressure must be exerted on 

 the elliptical egg-mass at a point above its minor axis thanbelow the latter. 

 This will tend to squeeze part of its substance, since it is at last enclosed 

 in an elastic capsule before shell formation takes place, into the lower or 

 larger end of the mass. In this way the ovoidal form of the egg seems to 

 have first arisen. The mechanism by which this is accomplished can, 

 liowever, be best understood by means of a diagram showing the manner 

 and conditions under which the forces involved cooperate. 

 If the wall of the oviduct Oo is supposed to conform to the shape of 



