Ryder.] ^^4 [April 21, 



at opposite poles of the yolk is in opposite directions. This could not 

 occur except under conditions of rotation of the yolk or true egg during 

 the early steps of its passage down the oviduct. The lamiuie of the cha- 

 laz;c are in a continuous spiral scroll such as is developed by a thin lam- 

 ina rolled upon itself, such as a scroll of paper. This would seem to 

 prove that a rotation of the forming egg was necessary in order to give 

 rise to the phenomena described. 



2. The membrana putaminis is deposited in the lower portion of the 

 oviduct. Its fibres are cemented together where they cross one another, 

 showing that they must be formed in a plastic condition. The putaminis, 

 moreover, is laminated, showing that, like the yolk, it is a secretion, the 

 laminiie of which are deposited in succession. It finally covers the entire 

 egg and albumen as a secondary egg envelope, and possesses certain char- 

 acteristic traits of figure, firmness and elasticity. 



3. From the beginning of the process of tlie development of the sec- 

 ondary egg envelopes in the oviduct there is circular constraint around 

 the yolk and albumen owing to the tubular shape of the oviduct 

 itself. The walls of the latter, press upon the contained egg somewhat 

 after the manner of a broad elastic girdle. This pressure around the egg 

 elongates the whole mass in the direction of the long axis of the oviduct. 

 If this pressure of tiie elastic walls of the oviduct were not associated 

 with peristalsis of the oviduct, in other words, were the forming egg to 

 remain at rest within the duct, it would be deformed only from a spherical 

 to an elliptical figure. This restraint is least at the ends of the mass 

 where it tends to be extended into the lumen of the duct. This elastic 

 annular compression of the forming egg within the oviduct may be re- 

 garded as the true cause of the deformation of the hen's egg towards a 

 stable elliptical configuration, while still in the plastic state. 



4. After the completion of the membrana putaminis a third homogeneous 

 laj'er is deposited upon the latter in which the shell is formed. This shelly 

 deposit consists at first of isolated circular nodules of calcareous matter, 

 that only become fused together at a late stage of their deposition ; when in 

 fact they commence to become crowded against one another and pressed into 

 close contact as they enlarge from within outward. Previous to this fusion 

 the shell is flexible, if an egg is prematurely laid with an imperfect shell, as 

 every farmer's boy knows. After the fusion of these minute calcareous 

 plates the shell becomes rigid, as seen in a fully matured egg. It is probable 

 that a certain ditferential of pressure has been maintained at opposite ends 

 of the egg during the formation ofthe membrana putaminis, the matrix of the 

 sliell, and the shell itself that is instrumental in giving to the hen's egg 

 and birds' eggs in general their particular forms. This differential of pres- 

 sure at opposite sides of the elastic girdle formed round the egg by the 

 oviduct is caused by the physiological necessity of propelling the egg 

 down the oviduct, or, in otlier words, is due to tlie fact that the egg is 

 moved along by forces developed within the wall of the oviduct itself. 

 As this difi'erential of pressure increases on one of the sides of the oviducal 



