218 ART HUE E. SHIPLEY. 



Fig. 41,— Transverse section through hind-brain of larva of fifty-two days. 

 V. h. b. Cavity of hind-brain, au. Ear. r. I. Recessus labyrinthi. Vll.g. 

 Ganglion of seventh nerve, d. I. Dorsal lamella, c. g. Ciliated groove, v. r. 

 Ventral ridge, v. Velum, ao. Aorta, br. v. Branchial vessels. Zeiss's A, 

 00. 3, cam. luo. 



Fig. 42. — Transverse section through region of sixth gill-bar of fifty-tvpo 

 days' larva, br^. Sixth gill-bar. sp. gl. Spinal ganglion, ao. Aorta, a. c. 

 Anterior cardinal, br. v. Branchial vessels, ao. v. Ventral aorta. X. g. 

 Ganglion in tenth nerve, d. I. Dorsal lamella, br. b. Skeleton of branchia 

 bars. m. br. Branchial muscles. 



PLATE XXI. 



Fig. 43.— Drawing of larva of fifty-two days. The notch in the liver, 

 behind the heart, is due to the large gall-bladder, through whose walls the 

 cesophagus is seen. This drawing was made by Mr, E, Wilson from the living 

 specimen. 



