Kofoid. — Development of Lima?:. 



PLATE VIII. 



Fig. 51. View of the ventral surface of a gastrula, showing blastopore and velar 

 projections. X 350. 



Fig. 52. View of the anterior face of the eleventh section from the anterior end in a 

 series of nineteen transverse sections of an embryo of the stage of 

 Figure 51, showing blastopore and velar projections. X 350. 



Fig. 53. View of the posterior ventral surface of a gastrula somewhat more ad- 

 vanced than that represented in Figure 51. X 300. 



Note. — A defect in the shading causes the floor of the median 

 groove (Wpo.) to appear elevated into a ridge. There is no such ridge. 



Fig. 54. View of the left face of the seventeenth section in a series of obliquely 

 sagittal sections of an embryo of the stage of Figure 53, showing cleavage 

 cavity at the posterior end of embryo. X 350. 



Fig. 55. View of the ventral surface of an embryo more advanced than that seen 

 in Figure 53, showing development of the cephalic vesicle and the foot. 

 X 490. 



Fig. 56. View of the right face of the tenth section of a series of twenty-three 

 obliquely sagittal sections of an embryo with blastopore in the poste- 

 rior position. X 350. 



Fig. 57. View of the anterior face of the eighth section, from the anterior end, of a 

 series of sixteen transverse sections, showing arclienteron, the velar 

 ridge and enlarged cells (cnch.) in the region of the future shell gland. 

 X 300. 



