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THE AMERICAN NATURALIST [Vol. XL 



The second class of abnormal c^^gs includes those in which a 

 normal yolk is received by an abnormal oviduct and in consequence 

 becomes covered with an abnormal set oT envelopes. This is 

 represented by eggs that are normal as to contents, form, and size, 

 but are contained in other larger eggs. Instances of this kind 

 have been described by Barnes ('63; '85), Fritsch ('95), Chobaut 

 ('97), and Gruvel (:01). Very likely the second egg described by 

 Supino ('97) belongs to this class, but the inclosed egg, though of 

 normal size, is said to contain an unusual yolk, indicating possi- 

 bly an ovarian abnormality. Here also should {)robably be placed 

 an egg recorded by F^re (:02) in which the inclosed yolk, though 

 apparently normal, is contained in a small amount of albumen 

 and what appears to be a tliick egg meml)rane, but is without a 

 shell. 



In most of the instances just cited, the enveloping eggs are of 

 two kinds. The first consists of shell, membrane, and albumen as 

 in the cases described by Fritsch, Chobaut, and Gruvc^l; and the 

 second possesses a yolk in addition to these parts, as in the eggs 

 recorded by Barnes and Supino. The exact method by which a 

 normal egg becomes inclosed in a second more or less complete 

 egg is not wholly clear; but a cliscussion of tliis (|ii(vsti()ii will be 

 deferred till the third class of eggs has been descrilx-d. 



In the third class of double eggs there is evidence of both ova- 

 rian and oviducal abnormalities. In examples of this kind the 

 inclosed eggs usually consist of shell and membrane containing a 



Vaillant ('75), Parona e (irassi ('77), de Man (78), Philippi 

 ('93), Schumacher ('96), Herrick ('99a; '99b, p. 409), and Kunstler 

 et Brascassat (:01); or inclosing albumen but without a yolk, as 

 in the first egg described by Supino ('97), and those (iescribed l)y 

 Herrick ('99b, p. 410), and (iruvel (:02). In tlii-. class two types 

 of inclosing eggs might be expe^cted: one witli a volk and one with- 

 out a yolk, but, strange to say, of the nine instance' in which the 

 descriptions are sufficiently t'nll to allow this p,>ii,t to Ix' ascer- 

 tained, the inclosing egg alwav^ con^iMcd of -hell, albnnien, and 



yolk. 



^Parona e Grassi (77), de Man (78). Philippi ( '93), Schumacher ('96), 

 Supino, two eggs ('97), Herrick, two eggs ('99 a; '99b), and Kunstler et 



