EXPLANATION OF PLATES I AND II. 



REFERENCE LETTERS. 



a anus. 



ab abdomen. 



af abdominal folds. 



6 blastoderm cells. 



bl blastopore. 



c cerebrum. 



ch chorion. 



d dorsal vessel. 



do dorsal organ. 



e ectoderm. 



ec edge of carapax. 



ey compound eye. 



ga germinal area. 



h hypoblast or entoderm. 



ht heart. 



i intestine. 



I labrum. 



m mesoderm. 



mo mouth. 



mp mandibular palp. 



na neural rudiments. 



oc median ocellus. 



og optic ganglion. 



ol optic lobes. 



os ostium of heart. 



p proctodeum. 



pg pigment. 



sg supraoesophageal ganglion. 



t thorax. 



ta thoracico-abdominal area. 



te telson. 



y yolk. 



The Roman numerals refer to the serial number of the appendages. 



Fig. 1. Section of the unsegmented egg of Crangon showing the 

 nucleus and protoplasm in a central position. 



Fig. 2. Section of an egg during the second segmentation, passing 

 through one of the dividing cells in which two nuclei are already pres- 

 ent. 



Fig. 3. Surface view of a stained egg with about sixteen segmen- 

 tation spheres. 



Fig. 4. Section of the egg shown in flg. 3. 



Fig. 5. Section of an early stage of the germinal area. 



Fig. 6. Section showing the migration of nuclei to one pole (ga) 

 of the egg. 



Figs. 7 and 8. Surface views of the egg and region of the blasto- 

 pore. Of these, fig. 8 is the earlier ; it was inadvertently turned around, 

 the anterior end being placed towards the bottom of the plate. 

 (152) 



