Physiology of Reproduction in Domestic Fozvl 343 



bird is determined in the oviduct. The yolk as it leaves the 

 ovary is spherical in form, except as it may be deformed through 

 the action of gravity. As it passes down the oviduct it is sur- 

 rounded by albumen, and finally at the lower end by the so-called 

 "shell" membrane, or membrana testacea. It is probable that 

 the egg is not given anything approaching its characteristic form 

 until after the formation of this membrane. As to exactly where 

 and how the egg is given its form by the oviduct there is some 

 difference of opinion and definite evidence is lacking. Szielasko 

 ('05), who has paid particular attention to this problem, after 

 reviewing the older literature of the subject expresses the opin- 

 ion that the egg is given its definite form in the uterus. He 

 says on this point (p. 289): "Das Geprage, welches die Eiform 

 der verschiedenen Species aufweist, kann in der Tat, wie Grassner 

 vermutet, nur von dem Uterus verliehen sein; denn solange das 

 Ei im Oviduct verweilt, ist seine Form variabel, da es jeder Um- 

 hiillung entbehrt. Die erste Hiille, membrana testacea ge- 

 nannt, wird dem Ei erst im untersten Abschnitt des Oviductes un- 

 mittelbar vor der Miindung desselben in den Uterus — im sogen- 

 annten Isthmus — umgelegt. Auch durch diese Membran wird 

 dem Ei noch keine bestimmte Gestalt gegeben. Diese resultiert 

 erst aus der Umlagerung der harten Kalkschale, welche im Uterus 

 geschieht. Hier ist also das formgebende Organ, hier muss 

 demnach die Untersuchung angreifen." 



This was also the early view of the matter. Wahlgren writing 

 in 1871 states as a matter of common opinion that: "Hier (i.e., 

 in the uterus) erhalt das Ei seine Schale und seine Form." 



The most recent worker in the subject, Thompson ('08), while 

 making the statement (p. 112), "The egg, just prior to the form- 

 ation of the shell, is, as we have seen, a fluid body, tending to a 

 spherical shape and enclosed with a membrane," which would cer- 

 tainly seem to imply that he supposed the definite shape to be given 

 to the egg in the uterus, proceeds to develop a theory of the method 

 by which the egg gets its form which seems, as he states it, to in- 

 volve the activity of nearly the whole oviduct in the process. 



Direct observation shows that after the membrana testacea is 

 formed, and before the egg passes into the uterus, it certainly is 



