AMAZON—AMNION 11 
b. Higher Nidicole—hatched in a helpless condition, blind ; 
mostly naked, and for a long time nursed in the nest, the 
food- yolk having been used up at birth :—Columbe, 
Striges, Accipitres, Psittaci, Coccyyes, Epopes, Halcyones, 
Cypselomorphx, Pici, Passeres. 
The two series a and 6 stand phylogenetically parallel to each other. 
AMAZON, a bird-fanciers’ name for a certain group of PARROTS 
belonging chiefly to the genus Chrysotis. 
AMBIENS is a muscle (so called by Sundevall, Férhandl. Skand. 
Naturf. 1851, pp. 259-269: abstract in Rep. Brit. Assoc. 1855, Trans. 
of Sect. p. 137) which, arising from the pectineal process of the pelvis, 
runs along the inner surface of the thigh, passes the knee as a 
string-like tendon, and then forms one of the heads of the deep 
flexor muscle of the second and third toe. The taxonomic value 
of this muscle has been much over-estimated since Garrod (P. Z. 8. 
1874, pp. 111-123) divided the Class into HoMALOGONATA, birds 
possessing an ambiens muscle, and ANOMALOGONAT&, or birds 
without such a muscle. The muscle is typically developed in 
Crypturi, Gallinz, Pteroclide, Gralla, Laridz, Colymbide, Stegano- 
podes, Impennes, Anseres, Accipitres, Coccyges ; it is absent in all 
Striges, Cypselomorphz, Halcyones, Epopes, Trogonide, Pici, Pas- 
seres, Herodii, Alcidz, Podicipedide ; it is very variable in Ratite, 
Pelargi, Tubinares, Columbe, Psittaci (see also MUSCULAR SYSTEM 
and INTRODUCTION). 
AMIDAVAD, otherwise AMADAVAT, or AVADUVAT, the 
name given to a well-known favourite cage-bird, Estrilda amandava 
(see WEAVER-BIRD), being a corruption of Ahmadabad, the name of 
a town in Goojerat whence, more than 200 years ago, according to 
Fryer (New Account of East India, &c., London: 1698), examples 
were brought to Surat. In his peculiar style he tells us (p. 116) 
that “they are spotted with White and Red, no bigger than Measles, 
the principal Chorister beginning, the rest in Concert, Fifty in a 
cage, make an admirable Chorus.” 
AMNION (a Greek word of doubtful derivation, used already 
by Aristotle). From either end of the body of the very early 
embryo grows out a fold which passes dorsally over the embryo, 
and unites above it with its fellow from the other end; between 
the two layers of this double fold, which is the amnion, extends 
the body-cavity, and receives the rapidly-growing ALLANTOIS ; the 
outer membrane of the allantois fuses with the outer double fold of 
the amnion, and forms the chorion, lining the eggshell (see EMBRYO- 
LoGY). The amnion affords one of the principal differentiating 
characters in the vertebrata ; Reptiles, Birds, and Mammals are as 
Amniota (Heckel, Anthropogenic 1874) opposed to se 
and Fishes or Anamnia. 
