PHYLUM VEKTEBBATA 



Bilateral symmetrical animals with segmentally arranged 

 mesoderm, with a central solid axis (Chorda dorsalis, extending 

 through the whole length of the body, from head to tail, hence 

 holocliordate), dorsally of which lies the tubular central nervous- 

 system, ventrally the gut; the respiratory organs arise from 

 the anterior portion of the gut. 



SUB-PHYLUM ACRANIA 



LEPTOCABDI A, Mueller = ACRANIA, Haeckel = 

 CEPHALOCHORDA, Balfour 



Chorda persistent ; without cartilage in the skeletogenous 

 layer. Monorhinal. 



Eespiratory gut with a permanent hypobranchial groove or 

 endostyle. 



Liver a hollow blind-sac. Kidneys represented by meta- 

 meric nephridia. 



Gonads consisting of numerous gonomeres. 



With a large peribranchial cavity, or atrium, into which 

 open numerous gill-clefts and nephridia. 



No skull, no vertebrae, ribs or other arches, jaws or limbs. 



Amphioxus, Yarrel. With right- and left-sided gonads. 

 Five species in European, West - Indian, Calif ornian and 

 Malay seas. 



Epigoniclithys, Peters. With right -sided gonads only. 

 Three species in seas of Tasmania, Torres Straits, and Ceylon. 



Asymmetron, Andrews. With right-sided gonads only. 

 Two species, Bahamas, Louisiades, and Loyalty Islands. 



