222 ANDREWS. 



EXPLANATION' OF PLATE XIL 

 [Figures drawn with Zeiss camera and lenses.] 



Fig. 54. Dorsal view of larva oi Nereis limbata, 50 hours old. x 175. 



Fig. 55. The same, eighty hours old, reared at Beaufort, N.C. x 175. 



Fig. 56. Young Nereis taken in tow-net, Beaufort, N.C. x 50. 



Fig. 57. Half of section across head of larva of Proccerea tardigrada, showing 



larval eye. x 750. 



Fig. 58. Dorsal view of above larva, x 250. 



Fig, 59. Section of provisional eye of larval Nereis limbata at stage shown in 

 Fig. 54. x 1775. 



Fig. 60. Section of definitive eyes of same, ninety-six hours after fertilization. 

 X 1775- 



Fig. 61. Section of eye of young Nereis seen in Fig. 56. x 1070. 



Fig. 62. Section of posterior eye of larval Proazrea tardigrada. x 750. 



Fig. 63. Maceration of same larval eye, showing lens, pigment granules, and 

 neighboring cells, x 1000. 



Fig. 64. Dorsal view of non-sexual form of P. tardigrada where head of male is 

 forming. Beaufort, 1884. X 50. 



Fig. 65. Section of epidermis of new-formed sexual head of same; the earliest 

 appearance of an anterior eye as elongated cells, one containing pigment, x 475. 



Fig. 66. Section of part of head of young Leprcea rubra, showing one of eye- 

 spots. Depigmented thirty-six hours in Grenacher's liquid, x 1020. 



Fig. 67. Section of one side of cephalic plate of a Polygordius larva. Depig- 

 mented in acidulated alcohol, x 1020. 



Fig. 68. The same, but not depigmented, x 1020. 



Fig. 69. Part of transverse section of new sexual head of Procarea tardigraaa, 

 representing one of the posterior eyes seen in Fig. 64. x 1020. 



Fig. 70. Longitudinal section of same, showing an anterior eye. x 470. 



Fig. 71. Section of eye and surrounding brain cells in a species of Spio. x 470. 



Fig. 72. Similar section from a species of Tomopteris. x 470. 



