588 MONSTROSITIES 



instance is described by Mr. H. K. Coale (Auk, 1887, p. 332), in 

 which a superfluous toe was loosely attached to the muscles of the 

 thigh of a Buteo latissimus. 1 Monstrous examples with four legs are 

 known in Fowls, Pigeons, Geese, Sparrows and the Goldfinch, the 

 supernumerary pair being sometimes correlated with a double vent. 

 A Chick preserved in the Cambridge Museum has the additional 

 pair of limbs attached to the end of the stunted tail. 



Supernumerary wings, articulating below the normal Avings, 

 likewise occur, but very rarely except the legs be also doubled, so 

 that the monster possesses eight limbs (Tiedemann, Anat. und 

 Naturgesch. Vogel, ii. p. 273). 



Many other malformations may be seen in various Museums, 

 but only a few need be here mentioned such as Chicks with two 

 bills, three wings and four legs ; Geese, Pigeons, and Pheasants 

 with two or three bills ; Chicks, Ducklings and Pigeons with two 

 heads. Occasionally considerable portions of the trunk are affected 

 by duplicity, producing not only two heads and necks, but two 

 vertebral columns and two bellies. Two hearts, within otherwise 

 normal bodies, have also been described in adult Fowls, Turkeys 

 and Geese. The Cambridge Museum possesses a nearly adult 

 example of a Duck which beside the two normal and functional 

 legs has an extra right leg of the same size as the others, but ending 

 in five complete toes. Another immature Duck has a cleft in the 

 middle line of the sternum, separating it together with the keel 

 into a right half and a left, in this respect continuing the embryonic 

 condition. Similar cases of arrested development are common, and 

 one, of a Pigeon, has been figured (Phil. Trans. 1869, pi. xxiii. fig. 

 172). In the same Museum is an adult male Turnstone (Strepsilas 

 interpres), which was in perfect plumage when killed, with only one 

 leg, and not the least trace, as ascertained on dissection, of the other. 

 Fowls may have their toes more or less united by a web, and Ducks be 

 without any web between their toes ; the last case is of some curiosity, 

 insomuch as such birds, as they swim, close their toes during the 

 back stroke, thus adapting themselves to their abnormal condition. 



Questions relating to abnormal excess of structure form what is 

 called Teratology, on which the works of M. Camille Dareste 2 and 

 Mr. Bateson 3 may be profitably studied. The former comes to the 

 following conclusions : Abnormalities are always due to modifica- 

 tions of the early embryonic development. Multiple heads are the 



1 The same gentleman also records a Dolidionyx oryziwrus having a horny 

 spur, of which he gives a figure (torn. cit. p. 333), " growing from the thumb tip " 

 of each wing. This may be compared with the examples already cited (CLAWS, 

 pp. 89, 90), but they scarcely belong to the category of Monstrosities. A. N". 



2 Recherches sur la production artificielle des monstruositts, ou essai de Terato- 

 genie experimentale. Paris : 1877. 



3 Materials for the Study of Variation. London : 1894. 



