OF BRYOZOA. 197 



that is, at the toe of the shoe, and from the convex and concave 

 curves of the U a row of hollow fringes (t to ft) projecting about 

 in the same direction as the first tube, and you have the outlines 

 of the general cavity of this animal. All three of these parts 

 are in open communication with each other; and it is here only 

 that the fluids, or rather fluid, of the body circulates. There is 

 nothing that otherwise resembles a circulatory system. If, now, 

 the U be divided right and left into halves, the line which sepa- 

 rates them may be projected in the form of an imaginary plane 

 so as to divide also the first tube, which is the body proper, into 

 halves. This we will designate as the axial plane ; and you will 

 find that the arrangement of the organization is in reference to 

 this plane. 



Going back to the U, now, there is to be seen between the 

 outer (ft, ft) and inner (t 2 ) rows of fringes, and immediately 

 opposite the toe of the horse-shoe, a round aperture (m) half 

 covered by a sort of lid (/). This is the mouth. From it the 

 intestinal canal projects into the depths of the body cavity, 

 and then doubles upon itself, and terminates (an) not far from 

 the beginning, without deviating either to right or left from the 

 axial plane. A knife passed along this plane would split the 

 digestive system, from end to end, into halves. The throat (ce) 

 extends about one fourth of the length of the body, and is shut 

 off from the stomach (st) proper, except during the passage of 

 food, by a sort of valve (st 2 ) which projects like a ring between 

 them. The stomach (st, st 1 ) occupies the next two fourths of the 

 general cavity, and preserves the same narrow proportions which 

 obtain in the throat ; i. e., it is a mere thick-walled tube. In- 

 stead, however, of being continued directly from the furthermost 

 point of its backward reach, it opens at its mid-length (at cl) 

 into a thick tube, which passes forward and debouches (an) at 

 the surface of the body, on the side next the two limbs of the 

 U, and about opposite to the mid-length of the throat (). 



All that has ever been discovered of the nervous system of 

 Bryozoans is a small, double-oval, or broad, heart-shaped mass, 

 (g-,) which trends transversely to the bilateral plane, and is situated 



