Structure of Mugelona. 419 



service to the animal in protruding its anterior region from 

 tlie sand into the surrounding water for aeration and food, 

 as well as forming a special fulcrum during the movements 

 of the snout and anterior region in boring. 



Behind the preceding each segment is furnished with two 

 rows of hooks on each side, all corresponding in structure, 

 viz. winged hooks with bifid crowns, the most anterior having 

 the larger wings. When the hooks are viewed in front the 

 wings form a complete guard by uniting in a translucent 

 arch superiorly. 



In the posterior region of the body a tuft of simple curved 

 bristles occurs as a kind of support to each pillar of the lateral 

 lamellae. Moreover, a very fine tuft of hair-like bristles, 

 only observed on careful examination in the living animal, 

 projects behind the pedicle of the lamella in the same region. 

 It is difficult to believe that such are the tips of the former, 

 yet no others can be seen in the mounted preparations. Such 

 are probably homologous with the curious hidden spicular or 

 asbestos-like bristles in Puiydora. 



In the first region of the body the bristles and processes 

 are situated at the extreme front of each segment, near the 

 segment-junction. The ninth series occupies a prominent 

 ridge near the middle of their extremely short segment. In 

 the posterior region the hooks are placed at first toward the 

 anterior margin of the segment ; they then gradually pass 

 backward till they reach the posterior border of each segment 

 laterally. 



The anatomy of Magelona may, for convenience, be 

 arranged under tlie following heads : — 



I. The Cutaneous System, including: 1, The Cuticle, 



and 2. The Hypoderm. 

 II. The ]\Iuscular System. 

 III. The Digestive System, including the Proboscis. 

 ■^IV. The Circulatory System. 

 *V. The Perivisceral Fluid. 

 VI. The Nervous System, 

 VII. The Tentacles. 

 VIII. The Reproductive System. 



* IV. and V. have already been translated in the Journ. Anat. & 

 Physiol, vol. xiii. pp. 331-343 (1879). F'urther remarks may by-and-by 

 be made, especially in connection with Prof. Penham's move recent 

 researches. 



