1 68 



DEVELOPMENT OF AMPHIOXUS. 



P eripharyngeal Ciliated Bands of Ammocoetes. 



Corresponding with the right and left peripharyngeal 

 ciliated bands which we described as proceeding from the 

 anterior borders of the endostyle in Amphioxus there is 

 a pair of ciliated grooves in the pharyngeal wall of Ammo- 

 ccetes which proceed from the anterior lip of the hypo- 

 branchial groove after the latter has become to a large 

 extent shut off from the pharynx by the above-mentioned 

 diaphragm. These grooves curve forwards and upwards 



Fig. 93. Young Amphioxus, after the metamorphosis, having eight gill-slits 

 on each side. From the right side. (After WlLLEY.) 



p,b. Peripharyngeal band. v. Velum ; shown separately below the main figure, 

 with rudiments of four velar tentacles, e. Endostyle, extending backwards to the 

 level of the fourth gill-slit, r.m. Right metapleur. 



in front of the gill-clefts (after the obliteration of the first 

 pair of gill-pouches), and then proceed backwards on either 

 side of the dorsal middle line of the pharynx as far as the 

 commencement of the oesophagus. Here they appear to 

 curve downwards again, and uniting together, extend for- 

 wards as a median ventral groove to the posterior lip of 

 the hypobranchial aperture. 



