184 F. X. WILLIAMS 



17. The embryo is at first almond-shaped, later the cephalic 

 lobes appear and it becomes more and more arcuate. Finally 

 the embryonic envelopes are ruptured, and the embryo reverses 

 its position, assuming a coiled one. 



18. The labrum is at first bilobed. The pleuropodia or first 

 abdominal appendages are hypodermal structures, at first leg- 

 like, but later glandular and mushroom-shaped. They finally 

 disappear in old embryos by sinking into the body. Their func- 

 tion is uncertain. 



19. The nervous system develops early. The neuroblasts are 

 not very regularly arranged. An outer and an inner neurilemma 

 is developed. 



20. The stomodaeum and proctodaeum are deep, thick-walled 

 invaginations. The midgut ultimately envelopes almost all the 

 yolk material. 



21. The primitive coelomic sacs are conspicuous, at first slit- 

 like they later become rounded. They are shut off in each 

 segment. 



22. The pericardial cells appear to be mesodermal. They are 

 of large size and differentiated even before the fat cells. 



23. A suboesophageal body is present. 



