PHYLUM VERTEBRATA 



Bilateral symmetrical animals with segmentally arranged 

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

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

 iolochordate), 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 



LEPTOCAKDIA, Mueller = ACRANIA, Haeckel = 

 CEPHALOCHORDA, Balfour 



Chorda persistent ; without cartilage in the skeletogenous 

 lyer. Monorhinal. 



Respiratory gut with a permanent hypobranchial groove or 

 endostyle. 



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

 leric nephridia. 



Gonads consisting of numerous gonomeres. 

 With a large peribranchial cavity, or atrium, into which 

 )pen numerous gill-clefts and nephridia. 



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

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

 irve species in European, West - Indian, Californian and 

 [alay seas. 



Epigonichthys, Peters. With right -sided gonads only. 

 ?hree species in seas of Tasmania, Torres Straits, and Ceylon. 

 Asymmetron, Andrews. With right-sided gonads only. 

 Two species, Bahamas, Louisiades, and Loyalty Islands. 



