456 MORGAN. 



DESCRIPTION OF PLATE XXVII. 



Fig. 42. Section of longitudinal ciliated band to show structure of pigment spot. 



Fig. 43. Surface view of eyes of Tornaria, Fig. 6. 



Fig. 44. Section of same, and in a parallel plane. 



Fig. 44'. Section of same, posterior to Fig. 44. 



Fig. 45. Antero-posterior section of apical plate of Fig. 6. 



Fig. 46. Surface view of mid-dorsal surface of larva at time of metamorphosis, 

 and older than Fig. 6. 



Fig. 47. Same of older larva. 



Fig. 48. Cross-section through mid-dorsal line in collar region of embryo between 

 Figs. 6 and 46. 



Fig. 49. Cross-section through mid-dorsal line in anterior collar region of Fig. 46. 



Fig. 50. Same through middle of collar region. 



Figs. 51-55. Series of cross-sections through dorsal nerve cord of young Balano- 

 glossus. Fig. 51, in anterior region of collar. Figs. 53-55, behind collar. 



Fig. 56. Section through anterior end of Tornaria, showing posterior-lateral and 

 mid-lateral areas, x and y. 



Fig. 57. Section through same region of larva during metamorphosis. 



