in the Fish Gallery of the Indian Museum. 1 1 



tion and form of the central nervous system : (3) the 

 pharynx and gill-clefts, with the endostyle and hypo- 

 pharvngeal groove : (4) the peribranchial or atrial 

 chamber (coloured pink) into which the water is swept 

 after it has been used in breathing : (5) the metapleural 

 folds, or hollow folds of skin that run on either side of 

 the body, right and left, from the mouth to the region 

 of the atriopore. 



As previously stated, Amphioxus has no place among 

 the Fishes, and is now generally regarded as the 

 representative of a separate branch of the Chordate 

 phylum. 



It differs from all the true vertebrates (1) in having 

 no brain or skull of any sort, and hence no true paired 

 eyes : (2) in the form of the liver, which persists as a 

 hollow pouch of the gut ; and in the absence of a pan- 

 creas ; (3) in having no true heart and no red blood 

 corpuscles ; (4) in the curious primitive form of the renal 

 organs, which recall the Annelid type ; (5) in the large 

 number of paired reproductive glands ; (6) in the curious 

 asymmetry, not merely . of the body, but also of the 

 muscles, nerve-trunks, olfactory organ, and anus. 



It further differs from all true vertebrates except the 

 Lampreys in having no true jaws and no branchial 

 bars. And it further differs from all Fishes in having 

 a vast number of gill-slits. 



CYCLOSTOMA. 

 Lampreys and Hag-fishes. 

 [Case 5.] 



The Cyclostoma have usually been included among 

 the Fishes, but they differ from all true fishes in having 

 no branchial bars and no jaws, in this last respect 



