Plate X. 

 Fig. 29. Showing the conditions a little more advanced than in the pre- 

 ceding figure, the optic fold covering a considerably greater portion of the 

 cephalic plate. The presence of the ectodermal pit is indicated, c. p., which 

 tends to extend as a fnrrow in the direction of the stomodienm. 



Fig. 30. Stage IX. Showing the increased growth and fusion of the 

 anterior portions of the optic fold which now nearly covers the optic and 

 cerebral ganglia, the position of the chelicerre which have come to lie on 

 either side of the rostrum, the closure of the anterior and lateral grooves 

 completing the formation of the anterior and lateral vesicles, and the 

 extension of the ectodermal pit to form the ectodermal furrow, re. f. 



