5388 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 wings, 
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, pl. 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? and 
Mr. Bateson ® 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 Dolichonyzx oryzivorus having a horny 
spur, of which he gives a figure (fom. 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 monstruosités, ou essai de Térato- 
génie expérimentale. Paris: 1877. 
3 Materials for the Study of Variation. London: 1894. 
