THE EMBRYOLOGY OF THE HONEY BEE 99 



mandibles, and the first and second maxillae, respectively. The 

 last or twelfth ganglion is also compound, probably also represent- 

 ing the fused ganglia of three segments. 



The respiratory system consists essentially of ten pairs of spira- 

 cles (Sp) and two longitudinal tracheal trunks (LTraT), one on 

 each side. The spiracles are arranged in two longitudinal rows, 

 one on each side of the larva, each trunk segment, from the second 

 to the eleventh inclusive, bearing a single pair. The spiracles con- 

 sist of plate-like thickenings of chitin. In the center of each of 

 these is an opening leading into a narrow and short tubular branch 

 which in turn connects with the longitudinal tracheal trunk of 

 each side. These traverse the entire length of the body, lying 

 between the mid-intestine and the body wall. At their anterior 

 ends each tracheal trunk bends around the anterior end of the 

 mid-intestine above the oesophagus to join its counterpart of the 

 opposite side, thus forming a closed loop. At the posterior end 

 of the mid-intestine the posterior ends of the longitudinal trunks 

 form a similar loop, which is situated below the hind-intestine. 

 The longitudinal tracheal trunks give off both dorsal and ventral 

 branches which arise near those leading to the spiracles. The 

 larger ventral branches join with the corresponding branches of 

 the opposite side to form a series of tracheal loops or commissures, 

 one of which is found in each trunk segment, from the first to the 

 eleventh inclusive. The dorsal branches split up into finer branch- 

 es which are distributed to the dorsal half of each segment. 



The heart (Ht) is a thin walled tube, slightly constricted at 

 the boundaries between the segments, and extending the length 

 of the trunk in the dorsal mid-line, above the mid-intestine. 



The rudiments of the ovaries (Ov) are seen as somewhat flat- 

 tened elongated bodies lying above the mid-intestine in the dorso- 

 lateral region of the seventh and eighth trunk segments and 

 extending half way into the ninth segment. 



After having briefly outlined the structure of the newly hatched 

 larva, the account of the development will be resumed with Stage 

 VIII, which follows immediately after the completion of the 

 germ layers (Stage VII). 



Stage VIII, 44-46 hours (Figs. Villa and b). In comparison 

 with the previous stage the germ band has increased slightly in 

 breadth and also in length. At Stage VII its anterior end barely 



