722 THE AMERICAN NATURALIST.  [Vor. XXXIV. 
from the membrana compacta extend to the tips of the folds 
and villi. 
In the upper intestine the submucosa is rather thin, and 
but a scant muscularis mucosa exists. In the region of the 
spiral valve the submucosa above the szrazum compactum is a 
little thicker, and a prominent muscularis mucosa is present, 
lying in a rather dense mass. There are in many places rather 
isolated muscle fibres of the muscularis mucosa going up into 
the villi, and the connective-tissue prolongations so character- 
istic of the upper intestine are not nearly so marked. The 
muscle fibres of the villi extend upwards longitudinally, and 
were, without doubt, derived from the muscularis mucosa, as in 
mammals and birds. At the very end of the intestine, where 
folds and villi usually cease, there is an abundant muscularts 
mucosa, there being many longitudinal, and possibly a few 
transverse, muscle fibres and bundles of fibres scattered irreg- 
ularly through all the dense connective tissue between the 
epithelium and muscular coats. 
_ In general, the cores of the villi and folds, also all the sub- 
mucosa above the stratum compactum, are composed of rather 
dense adenoid connective tissue. There are no lymphatic 
glands or patches of adenoid tissue anywhere in the intestine, 
but there are in many places areas of diffuse adenoid tissue, 
especially in the lower part of the intestine. 
Before leaving the submucous structures to go on with those 
of the epithelium, it may be well to speak of the elements 
composing the spiral valve. Macallum (86) states that in the 
spiral axis of Acipenser and Amia there is a large quantity of 
unstriated muscular fibres, which in Amia is aggregated into a 
single bundle. In Acipenser he states that there are several 
bundles arranged irregularly in direction and position, so it 1s 
almost impossible to conceive that they represent excessively de- 
veloped portions of the muscularis mucosa. In Amia, although 
sections at times seem to show nearly a uniform bundle of 
muscle fibres occupying the central part of the valve, other 
and most of the sections show clearly numerous more or less 
closely placed bundles of plain muscle, most of the fibres run- 
ning transversely, that is, nearly parallel with the free edges 
