198 



THE ORGANIZATION 



close to the anterior end of the throat, on the side facing toward 

 the limbs of the U, and therefore in the interspace between the 

 anterior (m) and posterior (an) ends of the digestive canal. 

 From this there are a few nervous threads which pass, in part, 

 right and left into the fringed arms, and otherwise into the throat 

 near the mouth. 



The reproductive system (s,f) is attached to the wall of the 

 general cavity, on the side opposite to the nervous centre, (,) 

 and consists of a more or less elongated mass within which the 

 eggs of various sizes are imbedded. 



The animal has the power of withdrawing into itself by 

 what is called invagination ; like the sliding of the tubes of a 

 telescope one within the other, or more properly, like the inver- 

 sion of the finger of a glove upon itself. This is accomplished 



by the aid of two long, complex muscles (r, 

 r 1 ) which extend, one on each side, from the 



' 



head to the bottom of the sheath (ek, ek 1 ) 

 w r hich encloses the organization. The sheath 

 of the species before us is peculiar on ac- 



ti 



a count of its jelly-like character; and as the 

 s& individuals live in a community, which has 

 id arisen by the budding of one from the other, 

 ek their combined sheaths form a large tremu- 

 lous mass, oftentimes six inches in width, 

 covering submerged sticks and the stems of 

 rl aquatic plants in slow streams and pools. 



The sheath of most of the Bryozoa is 

 more elongated than the one we have be- 

 fore us, and usually of a parchmenty, horny, 

 or coralline nature. This other figure (fig. 

 120) represents one, Fredericella, which 

 possesses a parchmenty sheath, (ek, tu,) and 

 Fig. 120. whose crown of tentacles (t, t l , t' 2 ) is a 



nearly perfect circle, but still shows a trace of that prepon- 



Fig. 120. Fredericella regina. Leidy, MSS. 25 diam. A profile view of one 

 of the individuals of a branching, compound, fresh-water Bryozoan. tu, the parch- 



