HABITS. 11 



name it has since been known. According to the strict rules of 

 zoological nomenclature this is incorrect, the generic nam: 

 Branchiostoma having two years' precedence over Amphioxus. 

 But, as so often happens in human affairs, the unwritten law has 

 triumphed over the written, and the almost universal custom 

 of zoologists has been to call the genus Amphioxus. From this 

 custom we shall not venture to depart in this work. 



Having thus entered our protest against a breach of con- 

 ventional rule which is made knowingly, we had almost said 

 wantonly, by all zoologists, we may proceed to consider the 

 actual position in the system of this remarkable creature. 

 Here fortunately there is no conflict between preaching and 

 practice,, between a pedantic conformity to rule and a lawless 

 adhesion to custom. For law and custom alike agree that the 

 position of an animal in the system shall be determined by its 

 natural affinities as revealed by a study of its structure and 

 development. Judged by this test there can be no question 

 that Amphioxus is closely allied to the Vertebrata and must be 

 placed either within that group or in close juxtaposition to it. 

 As our readers know we have adopted the latter 'course and 

 have placed Amphioxus in a special phylum of its own, equal in 

 morphological importance but very inferior in the number of 

 its members to the great phylum Vertebrata, and have applied 

 to it, out of a number of claimants,* the name Cephalochorda, 

 in allusion to the extension of its notochord into the anterior 

 part of the cephalic region. 



Amphioxus'f is a small, semi-transparent, colourless animal. 

 Its body is elongated, laterally compressed, and pointed at each 

 end ; and it may attain a length of two inches. . It is entirely 

 marine, and is found at moderate depths in many parts of the 

 world. It has a remarkable power of moving in sand, in which 

 it is usually partially buried, its mouth alone protruding. But 

 it is capable of swimming, and when removed from the sand 

 bends its body with great activity from side to side. The 

 mouth is an elongated oval aperture on the ventral surface 

 immediately behind the anterior end of the body. It is sur- 

 rounded by a number of delicate ciliated processes, the oral cirri. 



* Pharyngobranchii, Acrania, Leptocardii, etc. 



( The anatomical description refers, unless otherwise stated, to A. 



! atit8. 



