EXPLANATION OF PLATES I AND II. 



REFEKENCE LETTERS. 



l labi'um. 



m mesoderm. 



mo mouth. 



mp mandibular palp. 



na neural rudiments. 



oc median ocellus. 



og optic ganglion. 



Ol optic lobes. 



OS ostium of heart, 



p proctodeura. 



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. 



a 



anus. 



ab 



abdomen. 



«/ 



abdominal folds. 



b 



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 er entoderm 



ht 



heart. 



i 



intestina. 



nucleus and protoplasm in a central position. 



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

 through oue of the dividing cells in which two nuclei are already präs- 

 ent. 



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

 tation spheres. 



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



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



Fig. 6. Section shovving 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 tliese, fig. 8 is the earlier ; it was inadvertently turned around, 

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

 (152) 



