1893 ] -^^ < I Ryder. 



of the oviduct from x' to y must be greater tlian the sum of the first pair 

 representing the resistance developed by the walls of the oviduct from 

 y to X. It is this diflFerence of annular pressure thus developed between 

 x' and y along the curve and y and x along the remainder of the same 

 curve that is responsible not only for the energy which propels the egg 

 along the oviduct, but which also deforms it while in a plastic condition, 

 before rigid membranes are deposited over it, and causes it to permanently 

 assume the ovoidal figure so familiar to every one in the form of the hen's 



Pursuing the analysis further, the composition of forces developed from 

 x' to y would take the direction c. Those from y to x would take the di- 

 rection d. A similar set would be developed from the two inferior quad- 

 rants below x, but these we may neglect, since they are of the same value 

 exactly as the pair of antagonistic energies already considered and devel- 

 oped above the axis x. Since c > d the tendency will be for the mass to 

 be propelled in the direction of e and there will thus be a second compo- 

 sition of antagonistic forces in the direction ofe which will not only propel 

 the egg along the oviduct, but also tend to deform the egg-mass prior to 

 its becoming encased in a rigid egg-shell. 



The development of the figure of the eggs of birds is therefore in all 

 probability a purely dynamical problem or one in which energy is applied 

 in a definite manner to the plastic surface of a mass in statical equilibrium 

 within the oviduct. The moment motion is set up to propel the egg 

 through tbe duct the forces operative in determining the figure of the as 

 yet unformed shell depend upon the physiological activity and condition 

 of tone of the muscular walls of the oviduct which must first deposit the 

 membrana putaminis, the figure of which as a somewhat elastic closed 

 membrane is determined as here supposed. This in turn definitely deter- 

 mines the figure of the shell, which is deposited upon it. In this way it 

 can be shown that the interplay of energies developed by the soft parts or 

 oviduct have determined the conformation of a hard part or of the shell. 



The shell itself is, however, deposited by a process involving the devel- 

 opment of a statical equilibrium which is finally satisfied when the devel- 

 opment of the shell has been completed. What is meant here is that the 

 shell-matrix is a non-cellular colloidal body which has a strong attraction 

 for soluble, inert, earthy substances such as lime salts, circulating in the 

 fluids of the bodj'. These being particularly abundant, partly as excreta, 

 in the vicinity of the cloaca, near which the shell of the eggs of birds is 

 formed, the source of the supply of these matters is not far to seek. These 

 soluble but inert salts are attracted by this colloidal matrix which they 

 finally saturate when the shell may be said to be completed. 



The shell of the eggs of birds has therefore probably been developed 

 statogeneticaliy, while the figure of the shell has been developed kineto- 

 cenetically. Both factors are, however, ergogenetic, that is, form and 

 structure has here been developed by the expenditure of energy. 



Tliat there has been great variation in the mode of exhibition of the 



PROC. AMEE. PHILOS. SOC. XXXI. 141. 2 A. PRINTED JUNE 30, 1893. 



