No. 405.] THE INTESTINE OF AMIA CALVA. 725 
appear to be cilia in other parts are simply the striated border 
of the epithelium. This border is best marked above the 
spiral valve; it becomes narrower as the caudad end of the 
intestine is reached. 
The blood of the folds and villi in Amia is supplied by a 
capillary network which resembles the blood supply of the villi 
in higher forms. Large blood vessels run in the submucosa 
and send up branches into the folds and villi. With a villus 
there are usually three main trunks of arterioles going up into 
afine capillary network. When the projections join each other, 
there are numerous small blood vessels which connect, to a 
greater or less extent, the two almost distinct capillary systems. 
The blood supply of the more distinct folds is practically the 
same as that of the villi—a continuous network, usually sup- 
plied by about as many main trunks as if a number of villi 
occupied the same position. 
It will be seen from some of the preceding structures de- 
scribed that a very interesting condition exists in the form and 
structure of the enteric convolutions. The intestine of Amia 
presents an appearance midway between folds and villi, having 
some of both structures, the latter, in a way, developed from 
the former by unequal growth. The villi possess all the char- 
acteristic structures of villi of mammals and birds, as do the 
folds, but falling short of villi simply because of their extent or 
lack of separation. In some of the higher forms, to a limited 
extent, signs of a transition from folds to villi are found, as in 
the double projections which occur occasionally in the small 
intestines of rabbits. 
Villi have been described in a few species of Pices, but their 
presence is not usual in this class. However, it may be noted 
that in general the forms in which villi have been described are 
what are generally regarded as the higher teleosts. As villi 
are characteristic of the highest vertebrates, such as mam- 
mals and birds, it is not difficult to accommodate villi to the 
highest fishes. But how are we to account for the specialized 
condition of the intestine of Amia? Simply as follows : Amia 
is a very ancient form of vertebrate, one that has changed but 
little from the ancestral type, and, therefore, has had as a 
