ZOOLOGY. 589 



points, which may be regarded as tentacula. The larger 

 species have a distinct nervous cord. * The Gordius cannot 

 well take any other position than the present, although it 

 does live in a state of freedom. 



Order 2. Polypary Worms Hirudines. 



3505. Body cylindrical with branchiae in or upon the 

 tegument, blood red ; two ganglionic nervous threads 

 run along the ventral surface of the body, as in Insects ; 

 all are indeed androgynous. 



Here belong the Red-blooded Worms, as Hirudines, 

 Lmnbrici, Nereides, and Serpulae. 



Fam. 4. Tubularial Worms Dermatobranchiata. 



Body cylindrical. The branchia3 are only a vascular 

 network in the tegument. 



Here belong the Hirudines and Lumbrici. 



The Hirudines have a perfectly naked body, without 

 filaments and bristles, a perfect network of vessels con- 

 taining red blood within the tegument, an intestine with 

 an anus, both sexual parts androgynoid; posteriorly 

 they have a pad or sucker ; in the mouth there are mostly 

 maxillae, and upon the head simple eyes. 



The Naiades and Lumbrici have bristles in longitu- 

 dinal rows upon the sides of the body. The latter are 

 androgynous. The Naiades increase by division. 



The Thalassemae have a protuberant white body ; red 

 blood-vessels only upon the intestine ; mouth rostriform. 



These Worms stick in the mud, and are nourished by 

 it. They have here and there bristles, but which do not 

 form any longitudinal rows. They appear to absorb 

 water through the skin, and respire by the intestine. 

 They cannot, by reason of their red blood, range with 

 the Holothuriae. 



Fam. 5. Alcyonioid Worms Notobranchiata. 



Body depressed, with pedal filaments, tentacula and 

 branchiae in two longitudinal rows upon the back. 



These Worms all live in the sea, adhering mostly 

 upright in the earth, and have frequently annulate, 

 rigid tentacula, ocelli, and pairs of maxillae, like Insects. 



