108 ABNORMAL CONDITIONS OF THE OVA OF BIRDS. 



the peritoneal cavity. It appears that as each yelk was matured 

 it fell into the abdomen, and was ultimately absorbed, whilst the 

 oviduct poured out albumen and formed a shell, as it would if the 

 yelk had passed into its tube. The Hen, when killed, was ap- 

 parently perfectly healthy. Specimens of the eggs are preserved 

 in No. 467. 



Purchased, 1871. 



B. Of the Ova. 

 a. Twin Eggs. 



In these two yelks or two perfect Chicks are enclosed in a single 

 shell. Double-yelked eggs seldom produce two Chicks. Twin 

 Chicks are probably produced from single-yelked eggs. For 

 further remarks on these conditions see page xix. 



457. The egg of a domestic Fowl with two yelks. The shell is 



well formed, and the egg is larger than the normal size. 

 A portion has been cut away to show the interior. 



Hunterian. 



458. A similar specimen. Hunterian. 



459. The egg of a domestic Fowl containing one Chick. A twin 



Chick escaped from the egg ; both birds were then alive. 

 The one now in the egg, however, died immediately. 



Presented by W. D. Oliver, Esq. 



460. The egg of a Fowl containing two distinct and perfect 



Chicks. The alantois and yelk appear to have been single. 



b. Of the coverings of the yelk. 



Inflammation of the oviduct gives rise to deficiency of the cal- 

 careous covering of the egg, and to a fibrinous condition of the 

 albumen. In some cases, from causes at present unknown, the 

 shell-membrane is the seat of calcareous deposit. 



461. The shells of three eggs, in which the shell-membrane is 



the seat of calcareous deposit. 



462. The shell of a Hen's egg, in which the small pole of the 



albumen was prolonged into a short spiral and covered 

 with shell. It is probable that this specimen is due to 

 disease in a minor degree, similar to that which produced 

 the following abnormal eggs. 



Presented by Dr. F. R. Fairbank. 



