ANELLATA. 143 



than in the earth-worm, and the supra-cesophageal ganglion is rela- 

 tively larger, having to furnish nerves to both antennae and ocelli. 

 The pairs of ganglions developed upon the ventral chord correspond 

 ■with the segments of the body in number, and are very close together. 

 In the Eunice gigantea there are upwards of 1000 ganglia; but 

 this complicated condition of the nervous system is more apparent 

 than real, and, like the multiplication of the pulsatile sinuses of the 

 vascular system in the same animal, depends upon the vegetative 

 repetition of like parts without any mutual subordination in reference 

 to the performance of a special office. 



In the Aphrodita the body is broader and thicker than in other 

 Anellides, and begins to exhibit that concentration which characterises 

 its form in the higher Articulata. But the segmental nervous ganglions, 

 thougli more closely approximated, are yet not confluent at any central 

 part. The brain is heart-shaped, having its bilobed base turned back- 

 wards and connected in the usual manner by large oesophageal columns 

 with the inferior ganglion. The antennal nerves are continued from 

 the apex. The visceral nerves are given off from the oesophageal 

 circle, and pass to the upper surface of the intestine, and there swell 

 into a small ganglion. The sub-oesophageal ganglion is of large size, 

 and bifurcates anteriorly : the second ganglion is situated close by the" 

 first, and gives off' two pairs of nerves : the third to the fifteenth 

 ganglions send off respectively three pairs of nerves, the first of 

 which corresponds with the inter-ganglionic nerve in the earth-worm, 

 and supplies the branchial organs ; the second pair is distributed 

 to the ventral muscles; the third to the lateral and dorsal muscles. 

 The abdominal ganglions, which succeed the fifteenth, send off" 

 each two pairs of nerves, and gradually diminish and approximate 

 at the posterior extremity of the body. In this highly organised 

 Anellides the nerves may be distributed into those of special sense 

 (antennal), the excito-motory, the sympathetic or stomato-gastric, 

 and the respiratory. 



The power of repairing injuries and reproducing mutilated parts is 

 considerable in the Anellides, and especially in the species of Lum- 

 briciis and Nais, in which it has been variously and extensively tested 

 by the experiments of Bonnet and Spalanzani. A worm cut in 

 two, was found to reproduce the tail at the cut end of tlie ce- 

 phalic half, and form a new head upon the caudal moiety. Bonnet* 

 progressively increased the number of sections in healthy individuals 

 of a small worm (^Lumbricus variegatus^ : and when one of these had 

 been divided into twenty-six parts, almost all of them reproduced 

 the head and tail, and became so many new and perfect individuals. 



* CEuvrcs, vol. i. pp.117 — -N5. 4to. 1779. 



