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THE AMERICAN NATURALIST [Vol. XLVI 



renders the crayfish less conspicuous and it probably profits by 

 the arrangement in much the same was as do various shore- 

 crabs which are decorated with sponges, alga or ccelenterates. 

 Whether the water bug improves its chances against racial ex- 

 termination by the adoption of such a pugnacious protector it 

 may be too much to assume, but at any rate whatever the util- 

 itarian value of the habit it must be of the same nature as that 

 which obtains in the widely distributed genus, Zaitha. An ob- 

 servation of the manner of egg laying on the crayfish would be 

 of much interest. 



-Tames F. Abbott 



DOUBLE EGGS 1 



Under some such caption as the above there have appeared 

 from time to time in zoological literature various accounts of 

 anomalous eggs, chiefly of the common hen. These have nat- 

 urally elicited more or less popular interest, and various expla- 

 nations have been proposed concerning them. AVhile it is no 

 part of the present purpose to review the history of these phe- 

 nomena it may not be amiss to merely call attention to a few of 

 the more striking titles under which they have been described. 

 For example, Barnes ( '63, '85 ) has described cases under the title 

 "Ovum in Ovo"; and Schumacher ('96), "Ein Ei im Ei"; 

 Parker ('06), "Double Hens' Eggs"; and quite recently Pat- 

 terson (11), "A Double Hen's Egg," are typical of numerous 

 titles appearing in the literature. The chief purpose of the 

 notes which follow is to call attention to an earlier paper by the 

 writer ( '99) and to describe subsequent facts which have come 

 to his knowledge. The only reason for specially referring to 

 the earlier paper ('99) is that it seems to have been wholly 

 overlooked by later observers of these phenomena, and this is the 

 more strange in that both Parker ('06) and Patterson (11), to 

 whom the journal (Zool. Bull.) was quite familiar and access- 

 ible, make no mention of it. 



In Fig. 1, which is reproduced from the article just cited, are 

 shown the essential features of the first case which came to my 

 direct knowledge some time prior to the date of the paper in 

 question. As will be noted this presents a very clear illustra- 



1 Contributions from the Zoological Laboratory, Syracuse University. 



