532 KNOWER. [Vol. XVI. 



some insects. There was no caudal flexure in this specimen, 

 the hind end of the band turning part way over the pole. 



At the completion of the elongation of the embryo the 

 appendages have become quite long. The head is enlarged 

 and globular. The first maxillae are tri-lobed, and the second 

 pair less markedly so. In the abdominal region ten well-marked 

 segments have become established, each with a distinct pair of 

 appendages. No appendages are figured by Brandt on the 

 abdomen at the corresponding stage of Calopteryx, and none 

 of the figures of Graber to which I have referred exhibit such 

 well-marked rudiments in that region. 



From this stage until "revolution" the embryo undergoes 

 but little change externally, though the sides of the band grow 

 dorsalward, and the appendages elongate considerably. 



" Revolution " is accomplished as described and figured by 

 Brandt (3) (also see Korschelt and Heider {17), figures on 

 p. ']']']) for the Libellulid. The amnion and serosa fuse into 

 a single membrane at one point, only to tear open over the ven- 

 tral side of the embryo and retract dorsally, to finally form the 

 "dorsal-organ" at the back of the head (stages O and P, 

 PI. XXXII). The head of the embryo now slips up along the 

 ventral surface of the yolk to the anterior end of the Qg%, 

 while the tail end comes to lie beneath the micropyles at the 

 opposite end (see diagrams, PI. XXXII). The ventral surface 

 of the embryo is now entirely on the micropylar, ventral side 

 of the Q.g%, as was the case until after the closure of the 

 amniotic cavity. The embryo has, therefore, returned to the 

 orientation of its first rudiment, the germ-disc. 



The remaining processes, up to hatching, consist in the 

 closure of the body along the dorsal mid-line, the completion 

 of the appendages, and the continued development of the 

 internal organs. In the stages following "revolution," the 

 embryo increases so greatly in bulk that, just before it leaves 

 the ii.g^2,, this has become distended to a remarkable size as 

 compared with the unsegmented egg. 



