ON THE ANATOMY OF AMPHIOXUS LANCEOLATUS. 377 



The inferior ligament may be raised from the inferior surface 

 of the column in the form of a tough ribbon. From the sides 

 uf the column aponeurotic laminae pass off to form septa of 

 attachment between the muscular bundles ; and along the 

 mesial plane above the column, a similar lamina separates 

 the superior bundles of each side, and by splitting below and 

 running into the sides of the column, forms a fibrous canal for 

 the spinal cord. Foramina exist all along the sides of this 

 sanal for the passage of the nerves. A similar septum is 

 situated along the inferior part of the column, from the part 

 where the inferior muscular bundles unite at the anus, to the 

 extremity of the tail. Along the superior edge of the 

 aponeurotic septum, between the dorsal muscular bundles, and 

 stretching from the anterior point of the vertebral column to 

 a point beyond the anus, and half embedded between the 

 superior extremities of the muscles, is a series of closed cells 

 of a flattened cylindrical form, adhering firmly to one another 

 by their bases, so as to present the appearance of a tube 

 flattened on the sides with septa at regular distances. Each 

 of these cells is full of a transparent fluid, in the centre of 

 which is an irregular mass of semi-opaque globules, apparently 

 cells. This series of cylindrical sacs consists of the rudiments 

 of. interspinous bones, and probably of fin rays, and is 

 attached below to the fibrous intermuscular septa, half covered 

 on each side by the lateral muscles, and enclosed above by the 

 tegumentary fold which constitutes the dorsal fin. 



A similar series of cells, with the same relations, is 

 situated on the ventral surface of the body, and stretches from 

 the spot where the abdominal folds terminate, to a point 

 nearly opposite the termination of the dorsal series. 



tiji/.tntchiio-slcr/r/on. — The splanchno-skeleton consists of a 

 hyoid apparatus and a scries of branchial ribs, seventy or 

 eighty on each side Tin's division of the skeleton will be 

 described along with the respiratory apparatus, with which 

 it is intimately connei ted 



