AMPHIOXTJS LANCEOLATUS. 623 



the Mediterranean. Its usual residence is upon banks of sand, where it 

 finds both shelter and abundance of nourishment. like the Ascidians, 

 it seems to feed entirely upon infusorial organisms, either animal or 

 vegetable, which abound in the localities p. 3og 



that it frequents, and which it swallows, 

 just as the Ascidians do, by the instru- 

 mentality of the vibratile cilia with which 

 its mouth and branchial chamber are 

 richly provided. Such is the activity of 

 its movements, that, when dug up from 

 its hiding-place in the sand, if left loose 

 for a single instant, it buries itself again 

 with astonishing rapidity, and thus almost 

 instantaneously eludes the grasp of those 

 who attempt its capture. Although de- 

 cidedly a member of the vertebrate series 

 of animals, the Amphioxus can hardly be 

 said to possess a skeleton, so soft is the 

 condition of those tissues which, from 

 their arrangement, evidently represent 

 this structure ; still it is not difficult to 

 point out the arches of the lower jaw (fig. 

 309, a) and of the branchial apparatus 

 (d), as well as the structure and position 

 of the spinal column. 



(1669.) One of the most interesting 

 features in the anatomy of the Amphioxus 

 is, that the canal which encloses the 

 medulla spinalis presents anteriorly no 

 cranial expansion, but the dorsal cord 

 representing the spine extends quite from 

 one extremity of the body to the other, 

 projecting both behind and before con- 

 siderably beyond the lateral muscles of 

 the body, and extending anteriorly con- 

 siderably further forward than the oral 

 apparatus (a), or the anterior termination 

 of the spinal cord. 



(1670.) The mouth (fig. 309) is sur- 

 rounded by a cartilaginous ring, com- 

 posed of several pieces, each of which 

 gives off a prolongation to support the Amphioxus. 



cirri that surround the oral orifice. The buccal cavity is lined with 

 mucous membrane, and is densely ciliated, the ciliary action forcing 

 continuous currents of water towards the branchial chamber (d), or the 



