1880. | Development of Amphioxus Lanceolatus. 15 
the greater portion of the water, in which the food is brought 
into the canal, to escape into the branchium and be forced, by the 
contraction of the walls of this cavity, out through the branchio- 
pore once more into the surrounding medium. The esophagus 
is a short narrow portion of the canal, and leads from the pharynx 
directly into the stomach, which enlarges considerably in diame- 
ter, and extends straight back to the end of the branchium. Its 
walls are rather thicker than those of the other portions of the 
canal, and upon the inside the cilia are disposed in such a man- 
ner that when in motion they force the particles of food, which 
come into the receptacle, into a long rope-like body, and then 
cause this food-rope to revolve and twist about until all the 
nutriment and shape is twisted out of the component particles 
and the refuse material is forced on into the intestine. The food 
consists of diatoms, alga and most any bit of organic material, 
plant or animal, which is floating in the water in the neighbor- 
hood of the animals, and which can succeed in passing the 
guards and entering the stomach, and if a young animal is taken 
and placed in some water under the microscope, the entrance of 
these particles into the canal and their gradual grinding up as 
they get into this vortex of the stomach, can be readily seen 
through the nearly transparent tissue, and well repays a little time 
spent in such observations. Ordinarily these little bits—animals 
or plants—sail along down the canal without any hindrance from 
the guards, and as they approach the end of the “rope,” they 
commence rotating slowly about the sides, often, in the case of 
animals, making uncertain efforts to escape, until after rolling 
around for a time they are gradually pressed into the mass and 
twisted on to make room for the others which are continually 
floating in from the outside. Sometimes a long piece of an alga, or 
partially decayed bit of organic material, is drawn by the power- 
ful action of the cilia, with a quick rush, against the mouth ori- 
fice or into the mouth cavity ; then, with a motion which seems 
nearly instantaneous, the pharyngeal tentacles are brought for- 
ward with a sudden flap, the mouth aperture is widely distended, 
and the offending substance is thrown out of the body together 
with the water which was in the mouth cavity, after which the 
tentacles return to their normal position along the sides of the 
pharynx. This action is often repeated four or five times before 
the object is gotten rid of, as the action of the cilia tends to _ 
