390 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



the coelomic sacs at the anterior end surrounds the stomodaeal invagina- 

 tion and at first even covers its bhnd end. Some mesoderm also pushes 

 into the labrum and into the clypeal region. In a similar manner at the 

 posterior end residual mesoderm covers the proctodaeal invagination. In 



splm s 



yc 



Vc 



ent 





ster 



vm 



Fig. 346. — Scolopendra cingulata. Cross section of rump segment, (coel) Coelomic 

 sac. {dm) Membrana dorsalis. (ent) Entoderm cell, (p) Leg. (sin) Sinus, {splm) 

 Splanchnic mesoderm, {ster) Sternite. {ter) Tergite. {vm) Membrana ventralis. {yc) 

 Yolk cell. {Adapted from Heymons.) 



addition to the median masses of mesoderm, isolated mesenchyme cells 

 may be found along the median line. 



After the rudiments of the appendages appear, each coelomic sac may 

 ])e regarded as composed of three parts: the middle part whose cavity 

 extends into the developing appendage, a mesad projecting flattened part 

 with a cleft-like cavity lying under the anlage of the sternite, and a similar 

 lateral part lying under the anlage of the tergite. Figure 346 represents 



pren bl enl ap+ ini md mxl rnx2 



Fig. 347. — Scolopendra cingulata. Parasagittal section through head. Coelomic sacs 

 of antennal {ant), intercalary {int), mandibular {md), first and second maxillary {mx), and 

 preantennal (pr-cn) segments. (W) Blood cells. (en<) Entoderm. {Adapted from Heymons.) 



a cross section, before the flexure of the germ band, showing these features. 

 It will of course be understood that the definitive position in the rump 

 segments of the middle part having the rudiment of the appendage will 

 be lateral, the part under the anlage of the sternite will be ventral, and the 

 part under the anlage of the tergite will be dorsal. In the early stages of 



