230 



which such a monstrosity has been observed among the Crocodilia. 

 I have myself seen multiple embryos in the case of the common fowl, 

 where two or even three embryos on one yolk may occasionally be 

 found; and Gerlach (4) describes and figures numerous cases of 

 double and triple embryos in the chick and the goose, in which the 

 embryos lie in all possible relationships to one another. As far back 

 as 1832, Geoffroy Saint-Hilaire (5) published his great five volume 

 work, dealing chiefly with human monstrosities ; and multiple embryos 

 among the lower vertebrates have since been described by numerous 

 writers. 



As may be seen from the figure, the two embryos under dis- 

 cussion, while entirely distinct, lie so close together that their vascular 



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Double Embryo of the Florida Alligator.« 



areas are flattened against one another. The long axes of the embryos 

 proper lie nearly at right angles to each other, their relative positions 

 being accurately shown in the figure, which was drawn under a camera 

 lucida. The embryos are of approximately the same age or state of 

 development, although one of them is slightly larger than the other. 

 As well as may be judged from a surface view, they have reached 

 about the state of development of a chick embryo at the middle of 

 the second day of incubation. About fifteen pairs of mesoblastic 

 somites are visible, and the neural canal is practically enclosed. A 



