458 MORGAN. 



DESCRIPTION OF PLATE XXVIII. 



FlG. 58. Cross-section through young Balanoglossus. See Fig. 9, line 58, through 

 anterior collar region. 



Fig. 59. Same through base of proboscis above. See line 59, Fig. 9. 



Fig. 60. Same through base of proboscis. See line 60, Fig. 9. 



Fig. 61. Same through proboscis. See line 61, Fig. 9. 



Fig. 62. Same through anterior proboscis. See line 62, Fig. 9. 



Fig. 63. Portion of section through base of proboscis between 60 and 61. 



Fig. 64. Same as 58, through first pair of gill pouches. See line 64, Fig. 9. 



Fig. 65. Same as 58, through second pair of gill slits. See line 65, Fig. 9. 



FlG. 66. Same as 58, through posterior end of larva. See line 66, Fig. 9. 



