DWARF EGGS OF DOMESTIC FOWL. 32 1 



brane was first noted by Coste, 20 and has since been observed 

 by many investigators including the authors. Since the com- 

 pound egg was formed of two parts imperfectly separated by 

 a fold of membrane, they must have united after all of the 

 albumen was formed and before the whole of the first com- 

 ponent had passed into the isthmus. That is, this compound 

 egg evidently represents the union of a dwarf and a nearly 

 normal egg at the anterior end of the isthmus. 



Two other compound eggs where one component was a dwarf 

 and the other a normal egg have been produced at the Station 

 plant. In both of these cases the membrane of the yolk in the 

 normal egg was uninjured. In neither case was there any yolk 

 in the dwarf egg. The only visible nucleus in each case was a 

 mass of chalaza-like coagulated albumen fibers. 



2. Double^ eggs in which the enclosed egg and sometimes also 

 the enclosing egg was a dwarf egg. 



The double or enclosed eggs observed at the Maine Station 

 are described in a recent paper." 1 It seems necessary to 

 summarize here those cases in which one or both of the com- 

 ponents was a dwarf. In three cases a dwarf egg was included 

 within a normal egg. Evidently in each of these cases a dwari 

 egg was returned up the duct and meeting a normal yolk was 

 included with it in a common set of egg envelopes. 



In six cases a small dwarf egg was enclosed within a larger 

 dwarf egg. In one of these cases there was a drop of yolk in 

 the outer egg. In two there was a small amount of yolk in the 

 inner egg. In each case the dwarf egg was covered by egg 

 membrane, while in two it also had shell. Each of the outer 

 eggs had normal egg membranes and shell. In three cases 

 there were bunches of coagulated albumen fibers resembling 

 chalazae attached to the poles of the enclosed dwarf egg. The 

 complete egg records for two of the six birds show dwarf eggs 

 or nesting records, which suggest that there may have been ;i 

 permanent disturbance in the morphology or physiology of the 



20 Coste, M 1874. Histoire du developpement des corps organises. 

 Tome I, Paris. 



"Curtis, M. R. 1916. Studies on the Physiology of Reproduction in 

 the Domestic Fowl. XVI. Double Eggs. Biol. Bui. Vol. XXXT, pp. 181- 

 212. 



3 



