Tlate VII. 

 Fig. 23, Stage IV. Showing the partial coalescence of the two parts of the 

 rostral rudiment, the extension of the optic plate, o. ?>/., the formation of 

 a distinct coxal portion to the pedipalps, pdp. c, which forms the rudiment 

 of the mandibles. The increase in the number of neuroblasts in the cerebral 

 and optic areas, and their extension to the neiiromeres of the chelicer?e, 

 pedipalps, and the thoracic appendages, is apparent. 



Fig. 24. Stage V. The advances made in the development of the cephalic 

 plate are shown in the deepening of the anterior groove, ant. gr., and of 

 the lateral grooves, hit. gr., the shifting of the rostrum from the anterior 

 margin of the plate to a point between the cerebral ganglia, the more com- 

 plete union of the parts of the rostrum, and the beginning of the fold 

 which forms the roof of the cerebral vesicle, o. f. 



