G. A. DREW ON YOLDIA LIMATULA, SAY. 37 



Fig. 55. Median vertical section of an embryo about 90 hours old. (A portion of 

 the stomodreum was drawn from the next section.) 



Fig. 56. Transverse section of an embryo about 75 hours old, showing the in- 

 vaginations that form the otocysts. 



Fig. 57. Transverse section of an embryo about 70 hours old showing the 

 forming pedal ganglia. 



Figs. 58, 59 and 60. Successive transverse sections through the anterior portion 

 of an embryo about 95 hours old. 



Fig. 61. Transverse section of an embryo about 95 hours old, taken through the 

 otocysts. 



Fig. 62. Transverse section through the liver pouches of an embryo about 95 

 hours old. 



Fig. 63. Horizontal section through the liver pouches of an embryo about 95 

 hours old. 



Fig. 64. Median vertical section of an embryo about 10 hours after casting. 



Fig. 65. Transverse section of an embryo of the same age as the preceding. 



Fig. 66. Horizontal section through the dorsal portion of an embryo about 12 

 days old. 



