OF NEW ENGLAND. 293 
CHAPTER II. 
SECOND ORDER. Picaria. 
Tus order is a ‘ way-farer’s home,” established to receive 
those birds who do not belong elsewhere (in science, a poly- 
morphic group). The (North American) birds composing it 
are characterized by the combination of a bill without any cere 
or soft membrane, and one of the following features: tail- 
feathers ten; foot syndactyle by the union throughout of the . 
middle and outer toe; front-toes two in number. There are 
also certain internal and other features which are more or less 
characteristic. Either the bill or the toes always present cer- 
tain peculiarities. 
There is an important element in classification, which is 
often overlooked, that of latent features. These are frequently. 
undeveloped. For instance, the chief, and let us momentarily 
suppose, the only, difference between the typical thrushes and 
mocking-thrushes is in the tarsus, or so-called ‘‘leg.” In the 
latter group it is always scutellate (or divided into scales)—at 
least, in front; whereas in the former thrushes, when adult, it 
is “booted” (¢. e. without scales, unless near the toes). Yet a 
young robin with scutellate tarsi is no less a typical thrush ; 
his tarsi are virtually “‘ booted,” and will become so upon normal 
growth. Those of a young Cat-bird never will. Is not ab- 
normal growth frequently due to the persistent latency of 
normal features? As another example, the females of two 
closely allied species may be exactly alike in coloration, size, 
and structure. They may differ, however, in the latent power 
of producing distinct eggs; they may differ less in the latent 
instinct of building different nests, or still less in the latent 
power of producing eggs, many of which contain the germs of 
very distinct male birds. Hence the freshly laid eggs of two 
species may be indistinguishable except in latent, undeveloped 
features, though, since like produces like, they may be identi- 
fied through the parent-birds. 
