62 RAMBLES OF A NATUKALIST. 



in Germany. I have myself made this fish the 

 subject of a most careful investigation, and at the 

 present day we may consider its organisation as per- 

 fectly known. Yet while we have no difficulty in 

 asserting most definitely that it belongs neither to 

 the Mollusca, the Articulata, nor the Kadiata, it 

 scarcely merits the name of a Vertebrate. It has 

 hitherto been admitted that the essential characters 

 of this sub-division of the animal kingdom are the 

 presence of a vertebral column, a brain, a heart and 

 red blood, yet the Amphioxus possesses neither heart 

 nor brain, properly so called, nor any distinct vertebral 

 column, and its blood is entirely colourless. The 

 impulse necessary to make the nutrient fluid pass 

 through the circulatory circle is communicated to it 

 by large vascular trunks. The blood resembles that 

 of the Molluscs. The vertebral column is repre- 

 sented by a cartilaginous stem, entirely composed of 

 cells, and extending from the head to the tail. The 

 brain, which is not protected by the slightest appear- 

 ance of a cranium, is only distinguished from the 

 spinal cord by the direction of the nerves which 

 issue from it. The eye is entirely enclosed in the 

 interior of the tissues, but owing to their perfect 

 transparency, it is probable that the functions of 

 the organ of sight are not the less perfectly accom- 

 plished. This diaphanous character of the Amphi- 

 oxus enables us, moreover, to ascertain that it pos- 

 sesses a mouth, which belongs rather to the Mollusc 



the venous system, and on the manner in which the circulation of 

 the adult gradually succeeds that of the foetus. His Embryology of 

 the Cray FishAstacusJluviatilis is also a very remarkable work. 



