216 



Without a pancreas. 



Notochord and other parts of skeleton 



Cartilaginous. Skull with an in- 

 complete roof. A complex frame- 

 work (" branchial basket ") sup- 

 porting the gill-pouches. Skeleto- 

 genous tissue around notochord 

 develops neural arch rudiments. 

 Pins have supporting " rays." 

 Buccal funnel and "tongue " 

 have, respectively, an internal 

 supporting ring and rod of car- 

 tilage. 



Dorsal and ventral spinal nerve 

 roots not united. 



Without a sympathetic nervous 

 system. 



Olfactory organ is single. Nasal 



opening (nostril) is mid-dorsal, 

 on top of head. Hypophysis 

 (naso-palatine canal or pituitary 

 tube) opens anteriorly into olfac- 

 tory sac ; but its posterior end is 

 blind, and therefore it does not 

 communicate with buccal cavity. 



Eyes (without cornea). 



Ear consists of two semicircular 

 canals and sacculus. 



Heart and blood system fundament- 

 ally similar to that of Fishes. 



Pericardium ia not continuous with 

 main peritoneal cavity (in adult). 



Without a spleen. 



Pronephroa is vestigial in adult, and 

 opisthonephros is functional : and 

 its: ducts or ureters are pronephric 



ducts, which unite terminally to 

 form a urinogenilal sinus, opening 

 into the cloaca. 



Without a pancreas. 



Skull simple and without a roof. 

 " Branchial basket " rudimentary. 

 Nostril tube with rings of cartilage. 

 Barbules and " tongue " with in- 

 ternal supporting rods of cartilage. 



Dorsal and ventral spinal nerve 

 roots united. 



Without a sympathetic nervous 

 system. 



Nostril is dorsal, at anterior end of 

 head. Hypophysis opens anteri- 

 orly into olfactory sac, and pos- 

 teriorly into buccal cavity, just in 

 front of pharynx. 



Eyes very rudimentary and hidden 

 under skin. 



Ear consists of one semicircular 

 canal. 



As in Lamprey. 



Pericardium is continuous with 

 main peritoneal cavity. 



Without a spleen. 



Pronephros persists (partly) in adult. 



