150 THE VERTEBRAL COLUMN. 



longer be recognised in stage L. There can however be but 

 little doubt that they supply the tissue for the muscles of the 

 limbs. The muscle-plates themselves after giving off these 

 buds to the limbs grow downwards, and by stage L cease to 

 show any trace of what has occurred (PI. xii. fig. 1). This 

 fact, coupled with the late development of the muscles of the 

 limbs (stage 0), caused me to fall into my original error. 



The Vertebral Column and Notocliord, 



In the previous chapter (p. 107) an account was given of 

 the origin of the tissue destined to form the vertebral bodies; 

 it merely remains to describe the changes undergone by this 

 in becoming converted into the permanent vertebrae. 



This subject has already been dealt with by a considerable 

 number of anatomists, and my investigations coincide in the 

 main with the results of my predecessors. Especially the re- 

 searches of Gegenbaur* may be singled out as containing the 

 pith of the whole subject, and my results, while agreeing 

 in all but minor points with his, do not supplement them 

 to any very great extent. I cannot do more than confirm 

 Gotte's^ account of the development of the haemal arches, and 

 may add that Cartier^ has given a good account of the later 

 development of the centra. Under the circumstances it has not 

 appeared to me to be worth while recording with great detail 

 my investigations ; but I hope to be able to give a somewhat 

 more complete history of the whole subject than has appeared 

 in any single previous memoir. 



At their first appearance the cells destined to form the 

 permanent vertebrae present the same segmentation as the 

 muscle-plates. This segmentation soon disappears, and between 

 stages K and L the tissue of the vertebral column forms a 

 continuous investment of the notochord which cannot be distin- 

 guished from the adjoining connective tissue. Immediately 

 surrounding the notochord a layer formed of a single row of cells 

 may be observed, which is not however very distinctly marked''. 



1 Das Kopfskelet d. SclacTiier, p. 123. 



2 Entwicklungsgeschichte d. Unke^ p. 433-4. 



3 Zeitschrift f. Wiss. Anat. Bd. xxv., Supplement. 



4 Vide p. 138. 



