Kopoid. — Development of Limax. 



PLATE VII. 



Fig. 43. Young gastrula, seen from the posterior end, showing the broad shallow 

 blastopore. X 300. 



Fig. 44. The same, viewed from the ventral surface. X 300. 



Figs. 45-50. Sections of gastrula stage. Mesoderm cells shaded dark. 



Fig. 45. View of the posterior face of the ninth section from the posterior end in a 

 series of nineteen transverse sections, showing broad posterior portion 

 of the blastopore. X 350. 



Fig. 46. View of the posterior face of the fifteenth section in the same series, show- 

 ing the deepened anterior end of the invagination. X 350. 



Fig. 47. View of the right face (animal pole uppermost) of the eighth section in 

 a series of sixteen sagittal sections through a blastula containing eighty 

 cells, showing mesodermal pole cell and cleavage cavity. X 350. 



Fig. 48. View of the left face (animal pole above) of the eighth section of a series 

 of twenty sagittal sections of an early gastrula, at about the stage of 

 Figure 43, showing cleavage cavity and the mesodermal strand of the 

 left side. X 350. 



Fig. 49. View of the left face of the tenth section of the same series, showing at the 

 right the mesodermal pole cell of the left side. X 350. 



Fig. 50. View of the left face of the eleventh section of a series of seventeen 

 sagittal sections through an embryo of about the stage of Figure 43, 

 showing the mesodermal strand of the left side. A. Anterior; P. Pos- 

 terior. X 350. 



