196 



The Development of the Eye Muscles in Acanthias 



scribed by Vetter^ 74, and designated by him, muscle levator labii 

 superioris. He does not, however, give any reasons for this view. 

 Miss Piatt was able to trace this muscle only until it came to occupy 

 a position in close proximity to the inferior oblique eye muscle. She 

 believed, however, that the muscle was permanent. 



This outpocketing, as will be seen in the reconstructions, can readily 

 be folloAved until a 26 mm. stage (Figs. 4, 5, 6, F). At a 28 mm. stage 





O. S. V. 



^'^'i; 

 ■^ 



Int. Uec. 



O f 



■? o 



Fig. 7. — Optic vesicle, nerves and developing eye muscles of an Acanthias embryo, 

 27 mm. total length. Right side, medial view. The oblique lines indicate the parts 

 of the somites which are being converted into muscles. 



its walls are thin and enclose an extensive lumen. At a 26 mm. stage 

 its lumen has disappeared and its constituent cells have become elon- 

 gate and apparently muscular. The muscle is situated at this stage, as 

 Miss Piatt stated, close to the inferior oblique eye muscle. As will be 

 seen in reconstructions, it is nearly continuous with the thickened 

 ventral edge of the remainder of the visceral part. The cells of this 



