EXPLANATION OF FIGURES ON PLATES. 175 



Figs. 79-81. Transverse sections of an embryo 

 with two well-formed mesoblastic somites. Stage 

 of Fags. 42, 43. 



Fig. 79. Section through the region of the first mesoblastic 

 somite. 



Fig. 80. Section through the region of the undifferentiat 1 

 mesoblast fold, immediately behind the second mesoblastic 

 somite. 



Fig. 81. Section from the posterior third of the body. 



Figs. 82-85. Transverse sect ions from an embryo 

 with three mesoblastic somites. Stage of Fig. 44, 

 45. 



Fig. 82. Section from the region immediately in front of the 

 first mesoblastic somite. 



Fig. 83. Section from the region of the first mesoblastic 

 somite. 



Fig. 84. Section from the region of the second mesoblastic 

 somite. 



Fig. 85. Section from the region behind the third mesoblastic 

 somite. 



PLATE VIII. 



Figs. 86-92. Transverse sections from anembryo 

 in which the fifth mesoblastic somite is seen in 

 process of formation. Stage somewhat later than 

 that of Figs. 46, 47. 



Fig. 86. Transverse section immediately in front of the 

 region of the first mesoblastic somite. 



Fig. 87. Transverse section through the region of the first 

 mesoblastic somite. 



Fig. 88. Section through the boundary between first and 

 second mesoblastic somite. 



